Welcome to the lesson on Python Variables
What is variables?
In simple terms, variables are containers for storing data values. just like your cabinets where you can store things.
Creating Variables
Python has no command for declaring a variable. A variable is created the moment you first assign a value to it.
Variables
Variables do not need to be declared with any particular type, and can even change type after they have been set.
Casting
Variables do not need to be declared with any particular type, and can even change type after they have been set.
String Variables
String variables can be declared either by using single or double quotes
Case-Sensitive
Variable names are case-sensitive.
Variable Names
A variable can have a short name or a more descriptive name.
Rules for Python variables:
A variable name must start with a letter or the underscore character.
A variable name cannot start with a number
A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
Variable names are case-sensitive (age, Age and AGE are three different variables)
Legal Variable name
Illegal Variable name
Variables name with more than one word
Variable names with more than one word can be difficult to read.
Here's what you can do to improve the readability:
Camel Case
Pascal Case
Assigning Multiple values to a variables
Many Values to Multiple Variables
Python allows you to assign values to multiple variables in one line:
Caution: Make sure the number of variables matches the number of values, or else you will get an error.
One Value to Multiple Variables
you can assign the same value to multiple variables in one line
Output Variables
the print statement is used to output variables
To combine both text and a variable, Python uses the + character
the + character can also be used to add a variable to another variable
For numbers, the + character works as a mathematical operator:
If you try to combine a string and a number, Python will give you an error:
Global Variables
Variables that are created outside of a function (as in all of the examples above) are known as global variables.
Global variables can be used by everyone, both inside of functions and outside.
This example shows how you can create a variable outside of a function, and use it inside the function
If you create a variable with the same name inside a function, this variable will be local, and can only be used inside the function.
The global variable with the same name will remain as it was, global and with the original value.
Create a variable inside a function, with the same name as the global variable
Global keyword
when you create a variable inside a function, that variable is local, and can only be used inside that function
To create a global variable inside a function, you can use the global keyword.
If the global keyword is used. the variable belongs to the global scope
End of Lesson
You have to come to the end of the variables lesson.
Let's apply your knowledge by attempting the quiz