Variables store data under a name to be accessed later. They can be set in the program as a fixed value, as the result of an expression, or by prompting the user for input.
In Python, variable names must start with a lower case letter or underscore. Variables can contain only letters, digits, and underscores.
Camel Case: the first word starts with a lower case letter and subsequent words start with an upper case letter.
I.E. birthYear, thisIsCamelCase
Snake Case: all letters are lower case with words separated by an underscore.
I.E. birth_year, this_is_snake_case
Note: When using variables in expressions, be conscious of the variables' data types. For example, trying to subtract a string and an integer will result in an error.
Examples:
Initializing/setting a variable:
a = 5
name = "Craig"
pi = 3.14
Setting a variable as the result of an expression:
b = 5 + 6
Storing the result of an expression involving variables:
c = a + b
Prompting for user input and store as a variable:
d = input("How old are you?")