Complete Python Guide: From Basics to Real-Time Weather App

What's up everybody? In this video, I'm going to teach you everything you need to know to start coding with Python.

I've also included 20 different hands-on projects to help you learn. You can find the entire list in the description of

this video. Our final project will be a weather app that fetches real-time weather data from an API. Even if you've

never coded anything in your life before, I'll walk you through the basics, the ABCs of programming. If that

sounds good to you, then I encourage you to sit back, relax, and enjoy the show. This course doesn't cost you

anything, but if you would like to help me out, you can help increase its reach by hitting the like button, leave a

random comment down below, and subscribe if you'd like to be a fellow bro. Thank you. I appreciate it. I don't like

boring introductions, so I say we just jump right in. There's two things we'll need to download. The first is a Python

interpreter to convert our written code to machine code. We're going to head to python.org, go to

downloads, and download the latest version. We will open this executable. If you're on Windows, you'll

want to check this check box, add Python exe to path, and we will install now. The setup was successful. And that's all

you need to do to download the Python interpreter. The second download we'll need is an IDE, an integrated

development environment. Basically, a place where we can write code. For IDEES, there's two popular choices when

writing Python code. PyCharm and VS Code. If you already use VS Code, you can stick with that. Just be sure to

download the Python extension. I find PyCharm more beginner friendly if you've never coded before. If you would like to

use PyCharm, go to jetbrains.com/pycharm. And we will click this green download

button. There's two versions of PyCharm, the professional version and the community version. The professional

version is paid for. I would not recommend using it only because there's plenty of free IDE on the market. We'll

use the community edition, the free one, because I don't like to pay for things and I'm sure you don't either. Select

the correct download for your operating system. I'm running Windows. I will download

PyCharm. We will open this executable. Click next. You could select a destination folder. I'll keep it as

is. Next, I'll create a desktop shortcut, but you don't necessarily need to. Click

next. Install. And we'll just have to give it a moment. Okay, the setup is now complete.

I'll check this checkbox to run PyCharm when we close this window. After opening PyCharm, we're

going to create a new project. You can rename your Python project. I'll keep it as is. You can

select a location. Again, I won't change that. You can create a sample welcome script, but for this tutorial, we won't.

Let's select the latest Python version and create our new project. In the menu to the left, we're

going to create a new Python file. File, new, Python file. Let's name this file main.

But really you can name it anything and select Python file. Python files end with the py file

extension. We should have our main Python file within our Python project folder. Now we're going to print

something to the console window. Within our main Python file, we're going to write a print statement. So type print

add a set of parenthesis. Between the set of parenthesis, we will add a set of double quotes to print something or

single quotes. Either one. My own preference is double quotes. Normally in a programming tutorial, the instructor

would tell you to print something such as hello world, but we like to be different

here. Instead, think of your favorite food. In this case, I like pizza. I will print I like pizza.

To run our Python program, we will click the screen arrow to run our main Python file. We should have a console window

that displays our output. I like pizza or whatever your favorite food is. Let's print another line of code.

Let's print it's really good. By adding a second print

statement, we are printing a second line of code. Now we'll discuss

comments. The Python interpreter doesn't output comments. To write a comment, you use a pound sign. I like to call this a

hashtag. My comment will be this is my first Python program. Comments are used as notes for

yourself or for other people reading this code. If I were to run this code again, this comment is not displayed to

the output. We still have I like pizza. It's really good. All right, everybody. So, that is your very first Python

program. And in the next topic, we'll discuss variables. All right, everybody. We are moving on

to variables. A variable is a container for a value. There's four different data types. We'll discuss strings, integers,

floats, and booleans. Yes, I know that's a silly name. A variable behaves as if it was the value it contains. Each

variable should have a unique name. Let's say we have a variable of first name. To assign a variable, you use the

assignment operator of equals. For text, a string is a series of text. This can be double quotes or single quotes. My

own preference is double quotes. Why don't you type in your first name? This variable of first name will behave as if

it was this value, this series of characters. So to demonstrate this, I'm going to print my first name

variable. So place it within a print statement without quotes. That will print your first name. Now, you don't

want this within quotes because then you're literally printing the word first

name. You could use your variable along with some text by using what is called an F string. That's the easiest way to

display a variable. So, you type F then a set of quotes. The F means format. So, let's say the word hello.

Then we will add our variable. We will insert our variable into this text when using an F string. To do that, you need

a set of curly braces. Then insert your variable. So the result is hello, whatever your first name is. In my case,

bro. Let's create another variable. Let's say we have a variable of food. Food equals think of your

favorite food. For me, I will type pizza. Let's print the

following. You like add a placeholder. Again, I'm using an F string. Our variable of food. Hello,

bro. You like pizza. Let's create an email. Use your own email or make up

one. Let's say my email is [email protected]. Then let's print our

email. Your email is add a placeholder. Display our email variable. Your email is

[email protected]. So these are strings. I'm going to add a comment that these are strings. A string is a series of

characters. They can include numbers but we treat them as characters. Now we have

integers. An integer is a whole number. An example of this could be somebody's age. How old are they? According to my

YouTube statistics, many of you are between the ages of 18 through 24. Let's say that I'm

25. Let me zoom in a little. Your integer should not be within quotes because it would be a string. Then

technically if I would like to work with this variable again I'll use an f string. Let's say you are add a

placeholder display our age variable years old. You are 25 years old.

Another example of an integer could be a quantity. You are buying a certain amount of something. Maybe I am buying

three items. I wouldn't have half an item. This would be a float technically rather than an integer. We are buying

three of something. So let's print the following. You are

buying. Add a placeholder. display our quantity

items. You are 25 years old. You are buying three items. Another example of an integer

could be an amount of people. Let's say num of students like a classroom. There are 30 students in our

class. Then we will print your class has add a

placeholder students. We will display the number of students. Num of students. Your class has 30

students. Those are integers. They're whole numbers. And again, make sure they're not within quotes because then

technically they would be a string. integers we can use in arithmetic expressions. If they were strings, we

couldn't. Then we have floats. Float means floatingoint number. A float is a number, but it

contains a decimal portion. An example would be a price. What is the price of something?

$10.99. Let's print our price. Print. I'll use an F string. The price is add a placeholder. display our

price. The price is $10.99. Let's preede our placeholder with a unit of currency. I'll pick

American dollars, but feel free to pick something else. The price is $10.99. So, floats contain a decimal

portion. What about a grade point average GPA? Let's say my GPA is 3.2.

Then I will print your GPA is display our GPA. Your GPA is

3.2. What about a distance? A distance can contain a decimal portion. 5.5 kilometers maybe.

Then I will print you ran. Add a placeholder. Display our distance. Then I'll add km

for kilometers. Or you could add mi for miles, but I'll stick with kilome. You rand 5.5

km. Okay. Then we have booleans. A boolean is either true or false. Let's say we're a student. is

student equals. If we are a student, we could say that this is true. True starts with a capital T. If we weren't a

student, let's say we graduate, we could say that this is false. Again, the first letter is capital. Booleans only have

two options, true or false. So, let's say that I am a student. Then I will

print are you a student? Then we will display our boolean value of is

student. Are you a student? That is true. With boolean values, we really don't output them directly. You're more

likely to see them used internally within a program, such as when working with if statements. This is a topic

we'll discuss in the future, so don't worry. You may see if is student. If this variable is true, then we will

print the following. Now, we don't need to use an string. We're not going to insert any

variables. You are a student. If this were false, we can add an else clause where we will

print you are not a student. Our variable of is student is true. We will print the if statement.

You are a student. If this were false, we will print whatever is within else. You are not a student. Let's think

of a few more examples. Is something for sale like a car or a product of some sort? Let's say

that is true. I'll write another if statement. If for sale, if this variable contains true, we will do the following.

Let's print that item is for sale. Else if it's false, we will print

something else. That item is not available. For sale is set to

true. This variable is true. We will print that item is for sale. else if it were

false we print that item is not available. One more example. Let's say we have a

boolean variable of is online. Is somebody online? I will set that to true. If is online. If that's true, we

will print you are online. Else we will print you are

offline. Is online is set to true. We will print you are online. else if it were false we print you're

offline. All right everybody so those are variables. A variable is a reusable container for a value. There's four

basic data types for beginners. A string which is a series of text, integers which are whole numbers, floats which

are numbers but they contain a decimal portion and booleans which are either true or false. They're binary. Your

assignment in the comment section is to post four variables. Post a string, an integer, a float, and a boolean. Try and

think of a unique example if you can. And well everybody, those are variables in

Python. All right everybody, so we are moving on to type casting. Typ casting is the process of converting a variable

from one data type to another. We have various functions to convert a value or variable to a string, an integer, a

float or a boolean. Let's create some variables. We will create a name variable. Type in your full

name, an age, make up some age, a GPA for grade point average, let's say minus

3.2, and a boolean of is student. Are we currently a student? Let's say that's true. Now, you actually could get the

data type of a variable or a value by using the type function. Then pass in a value or variable. However, when I run

this, there's no output. So, I need a print statement. We will print what is returned by the type function. Get the

type of our name variable, then print it. So our name variable is a string

str. Our age variable is an integer and int GPA is a

float is student is a boolean. Using these type cast functions we can convert from one data type to another. Here's

how. Let's start with something simple. Let's convert our GPA to an integer. Currently, it's a float. I will reassign

GPA. Use the int function to type cast to an integer. Then pass in my GPA. At the end, we will print our

GPA. If we type cast 3.2 to a whole integer, what would the result be? A whole integer of three. We truncate the

decimal portion. Let's convert our age to a floatingoint number. We will reassign

our variable of age. Use the type cast function a float. Then insert our age

variable. Let's print our age variable. And it should be a floating point number

25.0. Now we'll cover strings. Let's type cast our age to be a string. age equals call the type cast function of

string str pass in our age variable. So the result is still going to appear the

same 25. However, it's a string not an integer. And to prove that I will enclose my age variable with the type

function. The type of variable age is a string. It would be the same as if we're taking

this number and enclosing it within quotes. So this would make a difference because let's say that I add one to age.

Age plus equals 1. Well, we would get a type error. Can only concatenate strings, not integers

to a string. However, if I were to add a string of one to the end, we would be

using string concatenation. So let's say it's my birthday and I add 1 to 25. Well, since we're working with strings

now, the result would be 251. I am 251 years old. So strings and numbers behave

differently. With numbers, we can use them within arithmetic expressions. Strings, not so much. We will take our

name variable and type cast it to a boolean. name equals call the typcast function of

bool pass in our name variable. This has an interesting result. So I'm going to print name.

Booleans are either true or false. If I type cast my string of text into a boolean that gives me

true. Now it really doesn't matter what I write here. If I were to change my name to a single character such as B,

this would still be true. If our string variable was empty, there were no characters within it, that would

actually give us false. We could use this to check to see if somebody enters in their name or not.

If somebody types in their name, then we type cast it to a boolean. If somebody skips entering in their name, that would

return false. We could reprompt the user to enter in their name again. All right, everybody. So, that is type casting. It

is the process of converting a variable from one data type to another. This is especially useful with handling user

input because user input is always a string. There may be at times where we want to convert it to an integer, a

float or a boolean. And well everybody that is type casting in Python. All right everybody, in this

topic I'm going to show you how we can accept user input in Python. We use the input function. It's a function that

prompts the user to enter in data and it returns the enter data as a string. Here's an example. To accept user input,

we will call the input function. When I run this program, we need to enter in data to our console

window like so, then hit enter. However, we need a prompt. We need to tell the user what we

want them to type in. So, let's ask a question. Our prompt will be within quotes. Let's say, "What is your

name?" Let's try this again. What is your name? I can type in something. Why don't you go ahead and type in your full

name, then hit enter. Now, with this input, we're not quite doing anything with it. The input

function is going to return some data as a string. We can assign it to a variable if we would like. Let's create a

variable of name. Name equals our user input. Then once we have our name, let's print a message. I'll use an fstring. We

will print hello. Add a placeholder. Then insert our name variable within that

placeholder. Let's try this. What is your name? Type in your name. Hit enter. Hello. Whatever your

name is. Let's try a different name. I will pick Spongebob. Many people are familiar with Spongebob. Hello,

Spongebob. This time we will ask a user how old they are. Let's assign a variable of age equals accept some user

input. We need a prompt within quotes. How old are you? Once we have our age variable, let's

print I'll use an f string. You are add a placeholder our variable age years

old. What is your name? Type in your name. How old are you? Let's say that I'm

25. Hello. Whatever your name is, you are whatever your age is. Years old. All right. So, let's say that it's our

birthday. Before we print our age variable, let's say happy

birthday. Since I'm not inserting any variables within this print statement, this doesn't need to be an F string.

You'll want to use an F string if you want to insert variables. Before we display the user's

age, let's take the user's age and increase it by one. We could say age equals age +

one. But there's one problem with this. Type in a name. How old are you? Type in an

age. And we have a problem. We have a type error. Can only concatenate strings, not integers, to

strings. When we accept user input, we store that input as a string. Before we increment our age by one, we'll need to

convert it to an integer. We can't normally use strings within arithmetic expressions. But we can do that with

integers and floats, though. After we accept some user input for our age variable, we could take our age variable

and type cast it as an integer, which we talked about in the previous lesson. So let's say age equals our age after we

type cast it then increment it by one. So type in your name type in an

age and we get this message hello your name happy birthday you are whatever your age is years

old. So strings we can't normally use with arithmetic expressions. We would have to type cast it to an integer or a

float. However, we could condense some of these steps. We're taking up an extra line to type cast our age as an integer.

What we could do instead is that when we accept our user input, we can enclose the input function within a type cast to

int. And that would work the same. Type in your name, type in an age, and this works the

same. And it takes less lines of code and is more readable. I would say when we accept user input, it returns that

input as a string data type. Then we just have to type cast it to another data type if we need to. And in this

case for age, we do. Now, we'll go over a couple exercises because it's important to practice what you've

learned. In this first exercise, we're going to calculate the area of a rectangle. We need to prompt the user to

enter in a length and the width of a rectangle. So we will create a variable of length.

We will accept some user input using the input function. What is our prompt? Let's say enter the

length. Let's do this with width. I'll just copy and paste what we have. Width equals enter the

width. So we have the length and the width. To get the area of a rectangle, we have to multiply the length by the

width. So let's say area equals our length variable. Now to use multiplication you use an asterisk.

We'll discuss different arithmetic operators in the next lesson. So we have length time width. That is the

area. I'm going to print our area because I need to test something. Enter the length. Let's say five 5 in 5 cm.

Doesn't matter. Enter the width. six, we get a type error. Can't multiply sequence by non-int non- integer of type

string. When we accept user input, it returns a value of the string data type. We can't use those strings in arithmetic

expressions. We're multiplying the length times the width. We would need to type cast them as an integer or a float.

Since we're working with basic geometry such as calculating the area, let's do float. So let's type cast our user input

as a float for both length and width. Okay, let's try this again. Let's say 5 * 6. The area that's returned to

us is 30. 30.0. This result contains a decimal. It's a floating point number, a

float. So when we print the area, I'll use an f string this time. The area is I'll add a placeholder. Display our area

variable. Let's add a unit of measurement afterwards. I'll pick centimeters. Now, since we're working

with areas, if we would like to technically be accurate. So, we could say to the power of two or we could add

a superscript. So, if you would like superscript 2 and you're on Windows, make sure num lock is on, hold alt, then

type on the numpad 0178. So, we have a superscript of two. Again, it's not really necessary for

this lesson. I just think it'd be cool to include it because then it's technically

accurate. All right, let's say that the length is 6.1 and the width is 7.2.

The area is 43.92 cm squared because we're working with areas. Let's cover a second

exercise. This time we will create a shopping cart program. Exercise two, we're going to create a shopping cart

program. We need three variables. An item, a price, and a quantity of those items. We will create a variable of

item. We will accept some user input. What item would you like to buy? What are we trying to purchase?

We'll keep the data type of the user input as a string. Then we need a price. What is

the price of each item we're buying? Use the input function. What is the

price? A price should be a floatingoint number. For example, we might have dollars and cents. We need a decimal. So

let's type cast our input as a float. Then a quantity. We will accept some user

input. Our prompt will be how many would you like? Quantities. They should be whole

numbers. Let's type cast our input as an integer. Then we will have a total. What's the total that we have to pay?

So, let's take the price of each item. Use an asterisk for multiply our quantity. Then, let's do a test run.

Let's print our total. What item would you like to buy? Let's say a pizza. What is the price?

$10.99. How many would you like? I would like five pizzas. and our total is

54.95. Let's say that before we display the total, let's print the following. I'll use an F string. You have

bought insert a placeholder. Display our quantity X item or items. I'll add slash

S. Then we will print I'll use an F string again. Your total

is display our total. What item would you like to buy? I would like to buy a pizza. What is the

price? $10.99. How many would you like? I would like nine pizzas. They're all for me.

I'm going to eat all of them. You have bought 9 x pizzas. Your total is 98.91.

Let's add a unit of currency before this. Pick unit of currency before displaying the total. I'll pick American

dollars. I would like to buy pizza. What is the price? $9.99. How many would you like? I would

like a dozen pizzas. 12. You have bought 12 x pizzas. Your total is

$119.88. All right, everybody. That is how to accept user input in Python. And we've covered a few exercises. In the

next topic, we're going to create a Mad Libs game. And that is how to accept user input in

Python. All right, everybody. In this video, we're going to create a game of Mad Libs. Not because we have to, but

because I want to. It would be a good exercise for us, just so we're more comfortable with accepting user input.

If you're not familiar with Mad Libs, Mad Libs is a word game where you create a story by filling in the blanks with

random words. So, we're going to create a story template. The story is going to be missing some components. We will fill

in those components with random words that we type in. Here's a story that I've written myself. Print. Use an F

string. Today, I went to a insert a placeholder zoo. For our placeholder, we'll insert an

adjective. We'll insert a variable named adjective. Adjective. Adjective one. You're going to get an English lesson

today, too. An adjective is a description of something. So, for our zoo, adjective one could be

expensive, large, dirty. An adjective describe something. We'll fill this in when we

accept user input. For our second print statement, let's print the

following. In an exhibit, I saw a placeholder. We'll include a noun. Noun one. A noun is a

person, place, or thing in English. Maybe a gorilla. A gorilla named Harambe, for

example. Print. Use an F string. Let's say our noun one whatever this is we can reuse

variables was we will create a second adjective adjective 2 we will be describing

whatever noun one is this person place or thing and we will insert a verb verb one a verb is an action such as running

or eating. Then for our last statement, let's print I was add a placeholder. We'll create adjective

three. Adjective 3 will describe us. Now we're going to fill in these variables by accepting user input. We're going to

fill in adjective one. We'll accept user input using the input

function. Enter an adjective. I'm going to add a reminder that an adjective is a description of

something. Then we need noun one. Noun one equals input. Enter a noun. A noun is a person,

place, or thing. Then we have adjective two. I'll just copy adjective one. Paste it.

Change one to two. Then a verb. Verb one equals input. Enter a verb. I want verb one to

be in current tense. I'll ask the user to end the verb with ing. Enter a verb ending with

ing. Then it's current tense. our person, place, or thing of noun one is currently doing something such as

eating. And then adjective three. And I'll just copy one of these adjectives. Adjective 3 equals input.

Enter an adjective. Okay. And then we are ready to run this. Enter an adjective. An adjective describes

something. I will say suspicious or some kids like to say sussy or sus even. I've also heard of

kids nowadays using the word skipy. Feel free to type in whatever you would like. It is your story after all. I'm going to

say suspicious. Enter a noun, a person, place, or thing. I like to poke fun at

Mark Zuckerberg. So, I'm going to say my person is Mark

Zuckerberg. Enter an adjective. That is a description. Angry. Enter a verb ending with ing. So,

it's current tense. Uh, screeching. Enter an adjective. Happy. Here's my story. Today I went to

a suspicious zoo in an exhibit. I saw a Mark Zuckerberg. Mark Zuckerberg was angry

and screeching. I was happy. That's our game of Mad Libs. It's a word game where you create a story by filling in the

blanks with random words. Also, post the output of your Mad Libs game in the comment section down below because I

really want to read them. I want to see what you guys came up with. And well everybody, that is a Mad Libs game using

Python. Hey everybody, in this video I'm going to show you all of the different math that we'll need throughout the rest

of the series. I have a lot to cover and I'll split this video into different sections. We'll cover some basic

arithmetic operators, built-in math functions, a few functions from the math module, and then a few exercises. Be

sure to look at the timestamps if you would like to skip ahead to another section. Let's begin with some really

easy stuff. We're going to cover some basic arithmetic operators. Let's say we have a variable

friends. Currently, you have zero friends. If you need to increment a variable by one, you could say friends,

the name of the variable equals the name of the variable again + 1. So, the plus sign is the addition operator. And I

think we do have a little bit of experience with that already. So if I were to print my variable

friends, guess what? You now have one friend. We could also shorten this line of

code. You could say friends plus equals 1. That would do the same thing. This is known as an augmented assignment

operator. That will give you the same result. I prefer to use augmented assignment operators just because they

take less text and I think they're easier to read. Now let's use subtraction. Friends equals

friends minus 2. So of course minus is the subtraction operator. Uh you have -2 friends. I guess if you were to use the

augmented assignment operator that would be friends minus equals 2. There you still have -2 friends.

Okay. Multiplication. Let's change friends to how about five. Friends equals

friends time 3. You now have 15 friends. Then the augmented assignment operator version of

this would be friends time= 3. So again you have 15 friends. Let's cover

division. Friends equals friends divided by two. So we have 2.5 friends. Somebody

was cut in half. We have half a friend. Maybe it's just their legs or torso or something. Then the augmented assignment

operator would be friends / equals 2. And the result is still the same.

Now exponents friends equals friends to the power of two. So friends is currently five. Friends to the power of

two would be 5 * 5 which is 25. The augmented assignment operator version of this equation would be

friends exponent equals 2 and again friends is 25. Then we have modulus. Modulus gives

you the remainder of any division. Suppose we have 10 friends instead of five. I will assign a new variable

remainder. Remainder equals friends. The percent sign is known as the modulus operator. It will give us the remainder

of any division. If I were to divide my group of friends by three, we will have one remaining. I'll store the remainder

within a separate variable. We would have a remainder of one. It's kind of like in class when the teacher says for

everybody in the class to go into groups of three, then there's always that one kid that's by themselves. That's kind of

the same concept. We're dividing our friends into groups of three. then the modulus will give you the remainder. If

we divided our group of friends into groups of two, well 10 divides by two evenly, so there is no remainder. So

that is the modulus operator. It's fairly popular to use this operator to find if a number is even or odd because

it will divide by two evenly if that number is even. If the remainder is one, that means that the original number is

odd. Okay, so yeah, those are some basic arithmetic operators. addition, subtraction, multiplication, division,

exponentiation, then modulus. Now what we're going to do is cover some built-in math related

functions. Suppose we have three variables x= 3.14, y =

4, z = 5. It doesn't matter if these are floating point numbers or whole integers. The first is the round

function. We have a variable named result. I'm going to round x. So there is a built-in round

function. After the set of parenthesis, we can add some value or variable to be rounded. So we will round x to the

nearest whole integer. Then print the result. So our result is three. So that's the round

function. With the absolute value function, we can find the absolute value of a number. Uh let's change y to be -4

instead of four. We'll take result equals abs which means absolute value of y. The absolute

value is the distance away from zero as a whole number. The absolute value of -4 is

4. Let's change y back to four. There's a built-in power function. result equals

pow. Then we'll need a base and an exponent. What's y to the power of 3? That would be 4 * 4 * 4, which is 64.

That's the power function. You can raise a base to a given power. The next two are really useful.

Using the max function, we can find the maximum value of various values. What's the maximum value between x, y, and z?

Then I'll just need to store this value. Uh results equals the max between x, y, and z. Well, the maximum value is

five. Otherwise, there's min. What's the minimum value between X, Y, and Z? That would be

3.14. Now, in this next section, we do have some very useful constants and functions from the math class, but we'll

need to import the math module at the top of our text editor. So, import math. If you need the value of pi, you'll type

the name of the math module.py. And I'm just going to print this. print

math.py. The value of pi is 3.14159 and a bunch of digits that come after. If you're working with physics, I

do know that people use the constant e a lot. We won't be using e in this video series, but if you ever need access to

it, just type math. E, and that will give you e, which is 2.71 something something something. I believe e is

known as the exponential constant. If you need the square root of a number, let's say result

equals math. SQRT, we can place a variable or a value within the square root function. Uh

let's say we have x again. x= 9. What is the square root of x? Then I will print whatever the result

is. The square root of 9 is three. That is the square root function. There's a ceiling function.

Result equals math dot seal. Seal will always round a floatingoint number up. Suppose x is

9.1. So 9.1 rounded up is 10. Otherwise there's floor which will always round a number down. result

equals math.f floor. Let's change x to 9.9. 9.9 rounded down is 9. Those are some useful math functions. Let's go

over some exercises. Okay, this first exercise we are going to calculate the circumference

of a circle. We'll need the help of the math module because there's some good functions in there. To calculate the

circumference of a circle, the formula is 2 *<unk> * r. Let's ask a user for a radius because that's what r is. We'll

accept some user input. Enter the radius of a circle. We will type cast the input as a

floatingoint number to calculate the circumference. Again the equation is 2 * pi. We can get

that from the math module times whatever the radius is. And the user is going to type that in. Then we will print

whatever the circumference is. Print. We'll use an fstring the

circumference is our variable circumference. Enter the radius of a circle. I'll enter

10, actually 10.5. Their circumference is 65.97. If you want to round and truncate

some of these numbers, we can use the round function. Round circumference, then round to a given

decimal place. I'll round to two digits. Again, 10.5 rounded is 65.97. You could add a unit of

measurement, too. Let's say centimeters 10.5 is 65.97 cm. All right, that is the first

exercise. For this next exercise, let's calculate the area of a circle. We'll import the math

module. We'll ask for a radius. Much like before, radius equals input. Enter the radius of a circle.

We'll cast our input as a floatingoint number. The equation for the area of a circle

is pi time radius squared. We could easily use the built-in power function to raise

our radius to the power of two. Then we will display the area. print. I'm using an F string. The

area of the circle is our area to some unit of measurement. Let's say centime

squared. Enter the radius of a circle 10.5. The area of the circle is 346.36. But I would like to round this

number to two decimal places. I'll use that round function and I'll place area and the

number of digits to round to within this function. Let's try that again. 10.5. The area of the circle is

346.36 cm squared. That is the second exercise. For this last program, we're going to find the hypotenuse of a right

triangle. The formula to calculate the hypotenuse of a right angle triangle is C equ= the square<unk> of A^2 + B^2.

We'll begin by importing the math module. We'll ask the user for the lengths of side A and

B. A equals input. Enter side

A. We'll cast the input as a floatingoint number. We'll do the same thing with

side B. B equals enter side

B. Now this part's going to be confusing. We'll calculate C. We'll need A^2 + B ^ 2. We'll take A to the^ of 2

plus B to the^ of 2. Then we'll need the square root of all of this. Whatever the result is, I

will surround this equation with math. Square root and that should give us our answer. Let's

print using an F string. Side C equals whatever C

is. So, enter side A three. Side B will be four. side C is five. All right, everybody. So, that was everything

related to some arithmetic operators and math related functions in Python. And in the next video, we're going to cover a

few things involving string [Music] formatting. Hey everybody, in this topic

I'm going to explain if statements. An if statement is used to do some code only if some condition we set is true.

Else we could do something else. It's a basic form of decision-m. If it's true, we do something. If it's not true, we

don't do it. Let's ask a user for their age. Age equals input. Enter your age. I will type cast

the input as an integer. Depending on what the user's age is, we can do one of a few things.

Let's pretend that the user would like to sign up for a credit card, but in order to do so, their age needs to be

greater than or equal to 18. Well, we can check that. To use an if statement, type if, then some condition. What would

we like to check? Let's check to see if the user's age is greater than or equal to 18. Then add a colon, then hit enter.

Any code underneath the if statement should be indented. Make sure to pay attention to that because that's easy to

miss. If the user's age is greater than or equal to 18, let's print you are now signed

up. If I were to run this code, I'll type in my age. I'll type 21. Hit enter. This statement is true. Therefore, we

will execute any code found within the if statement. You are now signed up. What if this condition was not

true? Let's say my age is 13. Well, nothing happens. If the condition we check is instead false, we skip over

this code. If you need to take a different course of action, you could add an else

statement. If this is true, do this. Else, we can do something else. Let's print a different

message. You must be 18 plus to sign up. I'll type in my age again. I'll say that I'm 13. Hit enter. You must be 18

plus to sign up. That's basically an if statement. Do some code only if some condition is true. Else you can do

something else entirely. It's a basic form of decisionm. The else statement is kind of like a last resort. We can check

more than one condition before reaching the else statement. We can add an else if statement which we just shortened to

e l i if meaning else if. else if let's check if age is less than zero then we'll print a different

message you haven't been born yet. Now if I run this code I'll say that my age is negative one.

This condition is false. We skip this code. This condition is true. Therefore, we will execute this code and we skip

the else statement. You haven't been born yet. Let's add another else if statement. You can add as many else if

statements as you want. Let's check to see if somebody's age is greater than or equal to 100. We'll print a different

message. Let's print you are too old to sign up. If I were to say my age is 111 years

old, well, it states you are now signed up. The reason that we didn't reach this part of our else if statement. That's

because this condition is still technically true. You do need to pay attention to your order of if and else

if statements. If I want to be sure that nobody over 100 is signing up, I should probably move this to the

beginning. If age is greater than or equal to 100, then else if age is greater than or equal to 18, we'll do

something else. Enter your age. I am 111 years old. You are too old to sign up. So

those are if statements. If some condition is true, do something. else if you can check something else. If no

above conditions are true, you could do something else entirely. It's kind of like the default. Here's another

example. We'll ask a user if they would like some food. Response equals input. Would you like

food? We'll have the user type in Y for yes or N for no. If our

response now to check to see if two values are equal, you would use double equals. If the response is equal to y,

then we will print have some food. The doubles equal sign is the

comparison operator. It will check to see if two values are equal. You don't want one equals because that's the

assignment operator. Python in this case thinks we're attempting to assign the character y to response. So for

comparisons use double equals else we can print no food for

you. So would you like food? I'll type y. Have some food. Let's try it again. I'll type no

and for no. No food for you. Here's a third example. We'll have a user type in their name. Name equals

input. Enter your name. If our name is equal to an empty string, that means they didn't type in

anything. So, let's yell at the user. You did not type in your name. Else we will print using an

fstring hello whatever the name is. Enter your name. I'm just going to hit enter. You did not type in your

name. Let's run this again. I'll type in my name. And we have executed the else

statement this time. Hello bro. So one important thing that you should know is the use of booleans with

if statements. Suppose we have some boolean variable named for sale. I'll set this to be true. Now using an if

statement you can just use the boolean variable in place of a condition because a condition would evaluate to be true or

false. We could just say if for sale if that's true then let's

print this item is for sale. Else we will print. This item is not for sale. For

sale is set to be true. This item is for sale. If this variable were

false, well then the item is not for sale. Let's try a different variable. How about

online? If online, the user is online. Else the

user is offline. So the user is offline. I'll change the boolean to

true. the user is online. So with if statements, you can either write a condition or you could

use a boolean. All right, everybody. So those are if statements. Do some code only if

some condition is true. Else you can do something else. It's a basic form of decision-m and those are if statements

in Python. Hey everybody, this is a remake of my Python calculator program for

absolute beginners. All you need to know to complete this exercise is just if statements and how they work. So let's

get started. For this exercise, a user is going to select an arithmetic operator. Operator equals input. We will

ask the user to enter an operator. This will be plus for addition, minus for subtraction,

asterisk for multiplication, and a forward slash for division. You could enter more than this, but I don't want

to make this exercise too complicated. We will create a variable of num one to contain our first number. Let's say we

would like to add two numbers together. What is the first number going to be? Enter the first

number. And let's do this with the second number. Num two. Enter the second

number. Let me show you something. I'm going to add num one and num two together. Num one plus num two. We'll do

a test run. Enter an operator. I would like to use addition. Enter the first number 10

and 11. Well, the result is 1,1. When we accept user input, they are string data types. What we've ended up

doing is string concatenation. We've concatenated the string of 11 to 10. That's why we ended up with 1,1. We'll

have to convert these two strings to be floating point numbers by type casting them as a

float. So enclose your input functions with a type cast a float. And now we should be able to add those two numbers

together. So let's add 10 and 11 and we get 21.0. 0. Depending on the operator that the user selects, we'll use some if

statements to determine that. We will check if our operator variable is equal to a character of

plus. And for now, I'll write pass as a placeholder. We'll get back to this later. Else if our

operator is equal to minus, we will use subtraction. And for now, I'll write pass.

Else if operator is equal to an asterisk for multiplication, we will multiply. Else if our operator is equal

to a forward slash for division, we will divide. If our operator is addition, let's create a variable of

result. Result equals num 1 + num 2. For subtraction, it's going to be num 1

minus num 2. Multiplication would be num 1 * num 2. Then division would be num 1 / num 2.

Then we just have to print the result. Print our result. Be sure to do this with each of

the else if statements as well. And let's see what we have. Let's add 5.5 +

6.9. That gives us 12.4. Let's subtract

420 minus 0.69. That gives us 419.31. Let's test

multiplication. Multiply 3.14 times 3.14, which gives us 9.8596.

8596. Then division. Let's divide 69 by

13. And that gives us a really long number. So you could round a number if you would like. We would enclose our

result within the round function. And we'll just update each of these print

statements. This will round to the nearest whole integer. So let's divide 420 by

13. Let's say that we would like three digits after the decimal. Within the round function, we could add comma 3 for

three decimal places. Enter operator. Let's use division. Divide 420 by

69. So that gives me 6.087. So, we can round to a given digit after a decimal. In this case, three

places. What if somebody types in an operator that doesn't exist, like the word

pizza? Then I will divide two numbers. Well, let's add an else statement. If somebody selects some

input that is invalid, let's let them know. I'll use an fring. Let's say that the operator that the

user has selected is not valid. And let's try this again. Enter an operator pizza.

Enter the first number 420 and 69. Pizza is not valid. Let's say is not a valid operator instead. That makes

more sense. Pizza will be my operator. First number is 420. Second number is

69. Pizza is not a valid operator. All right everybody. So that is a very simple Python calculator

program you can make as a beginner. Hey there, it's me again. In today's topic, we're going to create a

weight converter program in Python. This is an exercise that will follow up the lesson on if statements. We'll convert

pounds to kilog or kilog to pound. The user is going to decide. We will begin by creating a weight variable. We will

assign some user input. Enter your weight. We will convert this input into

a floatingoint number. So add that cast. Then we will ask for a unit. Is this weight in

kilogram or pounds? Input kilogram

or pounds. We want the user to type in either K for kilogram or L for pounds. And these are

capital letters, by the way. Using an if statement, let's first check to see if our unit is equal to a

capital K. That means the current weight is in kilogram. We need to convert that weight to pounds.

Let's reassign weight equal to our weight times

2.205. Else if unit is equal to L, we need to convert to kilogram. Weight equals weight divided

by 2.205. Else the user did not type in something that was valid. Let's

print using an fstring unit was not

valid. At the end of our program, we will print the new weight. I'll use an fstring. Your weight

is our new weight after it's reassigned. Now, we need a unit of measurement. This is what I'm thinking we'll do within our

if and else if statements. Let's reassign our unit. We're reassigning unit to be lbs for

pounds. Else if unit equals kgs for kilogram in our results, we will display our new unit. Let's take a look. Enter

your weight. Actually, I'm just going to make one change. I'm going to add colon space there. That's much better.

Enter your weight. Let's say I'm 180 lb. This is in pounds. I'll type capital L. Your weight

in kilog is 81.63. I think I'm going to round this. I will enclose the weight variable

within a round function. We will round to one decimal place. Let's try this again. Enter your

weight. Maybe I'm 81 kg. I'll type k for kilogram. Your weight is 178.6 lb. Let's make sure

that this else statement works, too. Enter your weight. 180

pizzas. Pizzas was not valid. So, we're still displaying our output. We would want to avoid that if somebody doesn't

type in a valid unit. So, let's cut this line. Then, paste each within the if and else if

statements. When we exit the else statement, we're not printing the output. So, let's make sure that this

works. Enter your weight. I am 180 pizzas. Pizza was not valid. All right, everybody. Well, that

is a weight converter program in Python. I thought this would be a helpful exercise now that we have finished the

section on if statements. And yeah, that is a weight converter program in Python. Hey everybody. In this topic, we're

going to create a temperature conversion program as an exercise. We'll begin by asking what the current unit of

measurement is. Unit equals will accept some user input. Is this

temperature in Celsius or Fahrenheit?

C slashF then we will ask for the temperature. I'll store the temperature

in a variable named temp meaning temperature. temp equals input enter

the temperature. Then we should cast our user input as a floatingoint

number. If unit is equal to C, I'll fill this in momentarily. I'm just going to write pass as a

placeholder. Else if unit is equal to F, we will do something else. Else, let's print something. Just

an error message of some sort using an F string. unit

is an invalid unit of measurement. Let's test this else statement. Is the temperature in Celsius

or Fahrenheit? What if I were to type K for Kelvin? I'll make up some temperature like 100. K is an invalid

unit of measurement. All right, we know the else statement works. Let's convert Fahrenheit to Celsius using this

formula. We will take our temperature equals 9 * our

temp / 5 + 32. I'll take all of this and use the

round function. We'll round to one decimal place. Then we will print the current

temperature in Fahrenheit. I'll use an F string. The

Temperature in Fahrenheit is our temp

variable degrees Fahrenheit. Let's test this if statement. Is the temperature in Celsius

or Fahrenheit? It is currently in Celsius. What is 33° in Celsius converted to

Fahrenheit? The temperature in Fahrenheit is 91.4°. All right, so this section is working.

Let's work on the else statement. Else, if our unit is currently in Fahrenheit, we'll convert to

Celsius. That formula is temp equals our temperature minus 32 * 5 /

9. Then I will round the result to one decimal place. Then we'll print the temperature in

Celsius. The temperature in Celsius is temp° C for Celsius. Is the temperature in Celsius

or Fahrenheit? It is currently in Fahrenheit. Enter the temperature. 91.4. The temperature in Celsius is

33.0°. Well everybody that is a simple temperature conversion program in

Python. All right people, we're talking about logical operators today. Logical operators allow us to evaluate multiple

conditions. We can link them together. There's three we'll discuss or and not. We'll begin with or. With or we can

check more than one condition. If at least one of those conditions is true, then the entire statement is true.

Here's an example. Let's say we have an outdoor event. And I will create two variables. One temp, meaning

temperature. Let's say that this is in Celsius, 25° C. Pick Fahrenheit if you would like. And I will create a boolean

variable of is raining. I will set that to be false. It is currently not raining. If the temperature is too hot,

too cold, or it's raining, then I will cancel this outdoor event. We'll write an if statement to check that. If our

temp short for temperature is greater than let's say 35 35° C then I'll use the or logical operator or if our temp

is less than zero or if is raining is true. If one of these conditions is

true, we're going to cancel our outdoor event. So let's print the following. The outdoor event is

cancelled. Else we will print something else. The outdoor event is still

scheduled. The temperature is reasonable and is raining is false. It's not raining. So we print the else clause.

The outdoor event is still scheduled. What if the temperature was really hot, like

36°? Well, the outdoor event is cancelled. What if it's cold? -5°. The outdoor event is canled. This

condition was true. Therefore, we execute the if statement. Or what if the temperature is reasonable, but it's

raining? Is raining is true. Well, then the outdoor event is still canled. So with the or logical operator,

at least one of these conditions needs to be true. If one of these conditions is true, you could consider the entire

statement true. Now let's cover and. With and, we can link two conditions together. Both

conditions must be true in order for that entire statement to be true. So again let's say we have temp short for

temperature and we have a boolean variable of is sunny. I will set that to be

true. We will check if our temp is greater than or equal to 28° and is it sunny. Is

sunny if it's hot and if it's sunny. If this is true, let's print the following. It is hot

outside. For fun, I'm going to add an emoji, but you don't have to. I just think it's more entertaining that way,

but you do you. And I will print it is sunny. Sometimes these emojis are

formatted differently. I'm just going to copy it from somewhere else. That's better. Currently, the temperature is 25

25° C and it's sunny. This condition was false, but this one is true. With the and logical operator, both conditions

must be true in order for us to execute this block of code. If our temperature was

30°, well, then both conditions are true. It is hot outside and it is sunny. Let's write a few more. Let's add else

if. Else if the temp is less than or equal to zero and is

sunny. We will print something else. It is cold outside. I'll change the

emoji and it is sunny. Let's set the temperature to be5°.

It is cold outside and it is sunny. Both these conditions are true. So we do this

instead. You can link as many conditions together as you would like. Let's see if our temperature is within a certain

range. Else if temp is less than 28 and our temp is greater than zero and is sunny. to check to see if something is

within a certain range. There is a shortcut too. PyCharm is recommending this. We can simplify chain

comparisons. So this effectively does the same thing. If 28 is greater than our temp and our temp is greater than

zero and it's sunny, then we will print it is warm outside rather than hot. and it's still sunny. So, let's say

our temperature is 20° C and it's sunny. It is warm outside and it is sunny. Now, we have the not logical

operator. It inverts the condition. We are checking to see if something is either not false or not true. So, let's

check to see if it's not sunny. Really, I'll just copy what we have and paste it.

else if not is sunny then that means it's cloudy and let's use a cloud

emoji. So basically not does the opposite of what you're looking for. We are checking if not is sunny. Is sunny

is false. Then this condition is true. Okay. Let's say our temp is 28. Is sunny is now

false. It is hot outside. It is cloudy. What if our temperature was zero? It is cold outside. It is cloudy.

What if the temperature was reasonable like 20°? It is warm outside. It is cloudy. So not

it inverts the condition. If it's true, it's now false. If it's false, it's now true. All right, everybody. So those are

logical operators. They allow us to evaluate multiple conditions. With or, at least one condition must be true.

With and, both conditions must be true. And not. Not does the opposite. It inverts the condition. We check if

something is not false or not true. And well everybody, those are logical operators in

Python. Hey everybody. So today I got to explain conditional expressions in Python. A conditional expression is a

oneline shortcut for using an if else statement. If you're familiar with other programming languages, this is also

known as the trinary operator. It behaves similarly. Using conditional expressions, we can print or assign one

of two values based on a condition. Here's the formula. Return X if our condition is true. Else return Y. Here's

a basic example. We will create a variable for number just num. Let's say our number is five. I'm going to print.

Then within our print statement, I will write a conditional expression following this formula. I'll just copy and paste

it. Let's check to see if our number is positive. Let's print the text positive if our condition. What are we checking?

Let's check to see if num is greater than zero. That means it's positive. If this condition is false, we will instead

print whatever comes after else. Else negative number is five, that will print positive. If our number was neg 5,

well, this condition would be false. We would instead print negative. Let's go over another. Let's check to see if our

number is even or odd. Let's set num to be six. This time I will assign the result

to a variable. Our result equals take our formula. Let's

assign even if our num modulus 2 is our number divisible by

two. Does that equal zero? Else return odd. Then let's print our result. R

result number is six that is even. If it's five then it's odd. assign even if our number is divisible

by two. Else return odd. Let's create variables A and B. A will equal 6. B will equal

7. Let's create a variable of max num equals. Follow our formula again. return variable a if a is greater than b

else return b between a and b which is the maximum number that would be b of seven let's find the minimum this

time min num a if a is less than b else return b the minimum number between 6 and 7 is

This time we'll take an age. Age equals 25. We will create a variable of status equals. Use our formula

again. Return a string of adult. If our age is greater than or equal to 18. Else return a string of child. Then we will

print our status. Our age is 25. that's greater than or equal to 18, we will print adult. If our age was 13, then we

are a child. We will instead return child. Let's work with the temperature. Temperature equals 30°

C. So that's hot. Let's create a variable of weather. assign a string of hot if our

temperature is greater than 20. Else we will return a string of cold. What's the weather outside today? Based on the

temperature it is hot. If our temperature was 20 then the weather is cold. Okay, last

example. We will work with a user role. I will set this to be admin. We will define a variable of access

level equals again follow our formula return the text of full access

if our condition of user ro is equal to a string of admin else we will return limited

access. Our user role is an admin. Let's print our access level and we have full access. But what if we were a

guest? Well, then we have limited access. All right, everybody. Those are conditional expressions. They're a

oneline shortcut for the if else statement. It's similar to the turnary operator in other programming languages.

Using conditional expressions, we can print or assign one of two values. based on a condition, you follow the formula

of return x if our condition is true, else return y if it's false. And well everybody, those are a few examples of

conditional expressions in Python. Hey everybody, in this topic I'm going to cover a few useful string

methods that you may be interested in. Then at the end of this video, we will work on an exercise where we will

validate some user input. As we know a string is just a series of characters. Let's ask a user for their full name.

Name equals input enter your full name. The first method I'll show you

well technically this is a function. The length function will give us the length of a string. How many characters is it?

we will find the length of our variable name after the user types in some input. This function returns an integer. I'll

store that result within a variable. Uh let's just say result. Then I will print whatever the result

is. Why don't you go ahead and type in your full name. The length of this string in my

example is eight characters. That does include spaces too. 1 2 3 4 5 6 7 8. If you ever need the length of a string,

there is the length function. Let's move on. If we were to type our variable name followed by a dot, we have access to a

whole bunch of different methods. We have the find method. The find method will return the first occurrence of a

given character, the position. Let's find any spaces. I'll store the result within a variable

named result. I will type in my full name. The first occurrence of a space,

that's what we set, is at position three. When working with indexes, we always begin with zero. This first

character would have an index of zero, then 1 2 3. That's why the find method returned three in place of four. Let's

find the first occurrence of a capital B. See, it's zero. How about O? For me, that would be two. So

remember, it's always the first occurrence. If you need the last occurrence, there is a different

method, which is R find. R meaning reverse. We will find the last occurrence of an

O that has a position of five. 0 1 2 3 4 5. If Python isn't able to locate a given character, it will return negative

1. Let's find any I don't know uh Q's. Python could not find any lowercase Q's. The rfind method will return

negative 1 if there are no results. We can capitalize the first letter in a string by using the capitalize function.

Name dot capitalize. This method will return a string. I will reassign that to

name. Then we will print our name capitalized. I'll be sure to type in my name, all

lowercase. Since this is all one string, only the first letter is capitalized, even though I'm including a first and

last name. The upper method will take all of the characters in a string. Then make them all

uppercase. Follow your variable that contains a string followed byupper. Then I will reassign the result

to my name variable to overwrite it. Enter your full name. All of the letters are now

uppercase. There is also lower to make all of the characters lowerase. Name equals name dot

lower. Yep. All the characters are lowercase. Now the is digit method will return either true or false. If a string

contains only digits, the result is a boolean, true or false. I'll store that within a variable named result, then

print result. So if I were to type in my full name, is digit returns false. There are

not only digits within that string. If my string was some combination of alphabetical characters and numbers,

this method will still return false. It only returns true if my string only contains

digits. I'll just type in 1 2 3. See that's true. That is the isdigit method. Otherwise, we have is alpha name

is alpha. The is alpha method will return a boolean true or false depending if a

string contains only alphabetical characters. I'll type in my full name. So, the reason that this came up false

is because my full name contains a space, which is not an alphabetical character. If I typed in my full name

excluding any spaces, this would now be true. Is alpha would also return false if my name contained any sort of digits.

Bro 1 2 3. And that is also false. That is the is alpha method. Now let's ask for a phone

number. Phone number equals input. Enter your phone number. With the phone number, they

typically contain dashes. Let's count how many dashes are going to be in somebody's phone

number. Phone number dot count method. Let's count the amount

of dashes. So, place a character within the count method. This method will return an integer. Let's store that

within a variable. Result equals phone number. Method. So, type in some phone

number. 1-23 4-56- 8901. We have three dashes within the

string. 1 2 3. That is the count method. We can count how many characters are within a

string. We also have the replace method. Honestly, the replace method is probably one of the most useful methods of

strings. We can replace any occurrence with one character with another. Replace. Let's replace any

dashes with maybe a space. This method will return a new string. I'm going to reassign this to our phone number

variable. Then print the phone number. Enter your phone number.

1-234-567-8901. So, here's my new phone number, but we've replaced all of the dashes with spaces. Even better yet, we

could eliminate all the dashes completely by replacing the dashes or another character with an empty string.

1-234-567-8901. Here's our new phone number without any dashes. We've replaced all dashes with an empty

string, no characters. If you would like a comprehensive list of all of the string methods available to you, you can

use the help function. Type in the data type string string. Then I will print whatever the result

is. Here's a bunch of methods you might be interested in in the future. Capitalize,

case, fold, center, count, encode, ends with, just to name a few. All right, everybody. Here's an exercise for you.

We will validate some user input. We would like a user to enter in a valid username. However, there's a couple of

rules. The username can be no more than 12 characters long. The username must not contain any spaces and the username

must not contain any digits. Let's assign a variable named username equals

input. Enter a user name. First, let's check to see if our user input is more than 12 characters

long. We can do that using the length function. we will find the length of our username. The length function returns an

integer. Let's check to see if the length of our username is greater than 12 characters. If it is, we'll print a

message. Your username can't be more than 12 characters.

else we will print using an fstring welcome whatever our username variable

is. Let's try it. I'll type in my first name, last name, then add a whole bunch of characters

afterwards. Your username can't be more than 12 characters. Let's type in something

that's under 12 characters. Yep. And that appears to work. Okay, so we have accomplished task

number one. Our username can't be more than 12 characters. Next, our username must not contain any

spaces. We can use the find method of a string. Username.find. We will find any spaces.

That's a character. If no spaces are found, this method will return -1. Using an else if

statement I'll add not if the find method of username

equals1. If the result is not -1 meaning we found a space we will print your username can't contain

spaces. I'll type in my first and last name. You might need to think of something that's underneath 12

characters. Your username can't contain spaces. So, we have accomplished rule number two. Three. Username must not

contain digits. We can use the is alpha method of

strings. The is alpha method returns a boolean if a string only contains alphabetical characters. So, let's copy

that. I'll add another else if statement not username is alpha. Then we will

print your username can't contain numbers. I guess

technically is alpha would check for spaces too, but I'd rather have that be handled within a different if statement.

All right, I'll type in a username. I'll include some digits. Your username can't contain

numbers. All right, I think we've accomplished this. Let me make up a username following these three rules.

Yep, it seems to check out. All right, everybody. And that is a few useful string methods that you may be

interested in. Hey everybody. In this topic, I'm going to explain string indexing.

Indexing allows us to access the elements of a sequence using a set of square brackets, also known as the

indexing operator. Using this set of square brackets, following a string, there are up to three fields that we can

fill in. We can access a starting point in the string, an ending point, and a step. Here's an example. Suppose we have

a credit card number. credit number equals and I'll just make up some number 1 2 3

4-5678-9012 dash 3456. Good enough. If I need the first character within the string, I can type the name of my string

variable followed by the indexing operator which is a set of square brackets. The first position has an

index of zero. Computers always start with zero. So that's why the first index is zero. Then I'm going to go ahead and

print this. Print credit card number at index of zero. That would be one. If I were to

change the index to be one, 0 1, that should be two. Index two would technically be

three. Then four is the dash within our string. As you can see here with the indexing operator, there's up to three

fields that we can fill in a start, end, and a step. If you have just one field listed without any colons, it's assumed

you're filling in the starting position. So now, what if you would like the first four digits of the

string? Well, we would type the name of our string variable indexing operator.

We'll need a starting index colon then an ending index. The first four digits would be zero colon 4.

Then I will print this. And I'm just going to turn this first line into a

comment. Yeah, there we go. We have the first four digits of our credit card number. 1 2 3 4. Just so you know, with

the ending index, this index is exclusive. This first number would be zero 1 2 3 4. So we did not include that

dash within the number. The starting index is inclusive. The ending index is exclusive. So you can omit the zero in

the beginning. You could just say colon 4. Python assumes the starting position will be the beginning of the string. So

that would work too. Let's get the next set of digits. 5678 credit number indexing operator.

Let's find where the starting index would be. 0 1 2 3 4 5 5 colon 6 7 8 9. Then we will print whatever is

here. The next set of digits is 5 6 7 8. Maybe we need the last 12 digits. Well, what we could do in that case, we will

take our string variable credit number. Set the starting index to be let's see 0 1 2 3 4

5 5 colon. If you need everything up to the end of the string, you don't need to list an ending index. Just be sure to

add that colon. Python then assumes you need everything up to the end of the string. So, I will print whatever we

have. Then we should have everything besides the first four digits. Yep. 5 6 7 8 9 0 1 2 3 4 5

6. You could also use a negative index. Credit number. If you need the last character in a string, you would

set the index to be -1. Then I will print this. Print credit number at index of

-1. That would be six. -2 is five. -3 is

four. -4 is three. And then5 would be that dash right here. Yeah, you can use negative indexes too. Let's talk about

step. Using the step field, we can access the characters in a string by a given step. We can count by twos or we

can count by threes. So here's an example. So let's take our credit number. If we're not filling in these

starting or ending fields, but we need a step, we would need two colons. Then Python is assuming everything from the

beginning of the string to the end. Then our step will be two. This will print every second

character within our string. Yeah, here we are. We have 1 3 dash 6 8 9 1 so on and so

forth. If I were to change the step to three, we would count every third character beginning with 1

4 6 dash 1 36. All right, here's a practical

example. Let's create a program to get the last four digits of a credit card number. I'm going to assign this to a

new variable. Last digits equals our credit

number indexing operator. So, we need the last four digits. Where would the starting index begin? Well, we could use

negative indexing. This last digit is -1, -2, -3,4. We will begin at -4 colon. We can omit the ending index.

Python assumes we need the rest of the string. Then really, that's all we need. So, let's

print. I'll use an fstring. Uh maybe some x's. Maybe we're hiding somebody's credit card number

except the last four digits. Okay. then variable last

digits. All right. And here's our credit card number where only the last four digits are visible. Hey, you know what?

Let's add one more exercise. Let's reverse the characters in the string. I'm going to reassign credit

number equals credit number. If we need the entire string, we don't necessarily need a starting index

or an ending index. But for the step, this will be negative. Negative -1 will reverse a string. Then let's print

whatever our new credit card number is. Print credit number. And yeah, there is our credit

number backwards. To reverse a string, you set the step to be -1. So yeah, everybody, that is string indexing in

Python. We can access elements of a sequence using the indexing operator which is a set of straight brackets. You

can list a starting position, ending position and even a step if you need to skip over characters. But yeah, that is

string indexing in Python. Hey everybody, in this topic I'm going to explain format specifiers.

Format specifiers when used in the context of an string, they allow us to format a value based on what flags are

inserted. Following your value, you would type a colon and then some flags. Depending on what flags you insert, it

will format your output a certain way. You could add decimal point precision, allocate space, zero pad values, left

justify, right justify, center align, all sorts of things. Let's have some practice. I'll create

three prices. Price one, price two, price three. Price one will be

3.14159. These values aren't in dollars and cents yet, but they will be. Price two will be

987.65. As you can see, I'm just making up numbers here. Price three is 12.34. Let's display our prices using

some fstrings. Price one is placeholder price 1. Then we will do this for price two

and price three. Price two is price two. Price three is price three. Within our placeholder following the value, we can

add a colon. Then some flags. Those flags are the format specifiers. They will format our value a particular way

depending on what we insert after the colon. To add decimal point precision, you would type after the colon dot then

the amount of decimals to be displayed maybe two then f meaning floatingoint number. Let's do that with price two and

price three colon.2f. Price one is now 3.14. Price 2 is987.65. Price three is

12.34. I think I'm going to add some dollar signs before the placeholder. Yeah, that's much better.

For less precision, maybe one decimal place, you can change the two to a one. So.1

F. Each number only displays one decimal. 0.1 6.3 whereas in 3F would display three

decimal places.142 650.340 even though price 2 and price 3

only have two decimal places in the original numbers we will concatenate some additional zeros to allocate space

to display a value after the colon add some number some number for that many spaces how about

10. Each value now has a total of 10 spaces to display the output. 1 2 3 4 5 6 7 8 9

10. If you were to preede a number with zero, well, these numbers would be zero padded. Each number is now zero padded.

To left justify a value, you would use a left angle bracket. All these numbers are now left

justified. Then we have all of the space after. They're all uniform. Right justify would be a right angle

bracket. And I believe that's the default. Center align I believe is the carrot symbol.

Yep, our numbers are now centered. If you have any positive values and you would like to display a

plus sign, just use plus. Any positive number is preceded with a plus sign. Any negative number is

preceded with the negative sign. Or you could use a space for any positive numbers. So, colon space

These numbers are lined up evenly even though we have a negative number in here. There is a thousand separator

which is a comma. We should probably increase the value of our

prices. 3,00 9,870

1,200. Each thousand's place is now separated with a comma. We could also mix and match flags. I would like a

thousand separator along with decimal point precision of two decimal places. And why not? I will preede each

number with a plus sign if it's positive. Yep, here we are. So based on what you're looking for, you can add

some combination of flags. So yeah, those are format specifiers. everybody. Within your

placeholder, insert your value, a colon, then certain flags based on what you're looking for

exactly. But yeah, those are just a few format specifiers in Python. Hey everybody, in this topic,

I'm going to explain while loops. A while loop will execute some code while some condition remains true. Here's an

example. We'll use an if statement first. We will ask a user for their name. name equals

input. Enter your name. If our name is equal to an empty string, that means the user didn't type

in anything. Let's print a message. You did not enter your name. Else, we will

print using an string, hello, our user's name. If I were to skip this

prompt, we would execute this if statement. Then we continue with the rest of the program. What if I would