Basics

In this lesson, we will cover the basics of data types and variables.

Literal Constants

literal constants are values written directly into your code. They can be one of several different data types: int, float, and str.

# An integer is a whole number
1 
1245
-500

Printing

The print function is used to display text output from code. It takes a single argument as input, which can be any of the literal constants we just learned about.

print("This is how you print")
print("I can print more with another print call")

Comments

Comments are text inside your code that does not run. These are used for documenting your code, taking notes, and preventing certain sections of your code from running. In Python, a comment starts with the # character.

# This is a comment
print("hi") # this is also a comment

Exercise

Use the print function to print the following values: 123, 1.234, Hello, World!. You can do this with 3 separate print calls, each on a new line.

Exercise

Try using comments to prevent the print function from running in the first two lines.

Variables

Variables are used to store values like the literal constants we learned about earlier.

whole_number = 25
number_with_decimal = 1.245
say_hello = "Hello, World!"
five = 5
one_half = 0.5
message = "This is a message"
number_1 = 1

Variables are created by assigning a value to a name. This can be any combination of letters, numbers, and underscores, but the first character cannot be a number. The standard naming convention is to use lowercase letters and underscores to separate words. For example, my_variable_name.

Printing a variable is like printing a literal constant, except you use the variable name instead. You can print multiple variables by separating them with commas.

my_variable = 123
another_variable = "hello"
print("This is my variable:", my_variable)
# This is my variable: 123
print("and this is another variable:", another_variable)
# and this is another variable: hello

Variables can also be reassigned to a new value.

my_name = 'John'
my_name = 'Jane'

Variables are loosely typed, meaning Python will automatically determine the type of the variable based on the value you assign to it. This means you could have a variable that is a string one moment, and an integer the next.

my_variable = "One Two Three"
my_variable = 123

Exercise

Create a variable with an integer value, a variable with a float value, and a variable with a string value. Print all three on a single line. Additionally, reassign the variable existing_variable to a new value.

Print Formatting

An f-string is a way to format a string with variables, this can be useful when printing a message in a specific format.

name = "John"
age = 25
print(f"Hello, my name is {name} and I am {age} years old.")
# Hello, my name is John and I am 25 years old.

You can also add formatting to the variables.

pi = 3.14159265359
print(f"pi is {pi:.2f}")
# pi is 3.14

User Input

The input function is used to get input from the user. Normally this would be through the command line, but for this course, it will be through a popup text box. The input function produces a string from the user input. You can also include a prompt message to display to the user.

query = input("hello, how are you today? ")

Exercise

Using the input function, prompt the user for their name and store it in the variable name.