Python Tutorial
Python - Introduction Python - Syntax Python - Variable Python - Number Python - Casting Python - String Python - Operators Python - Conditions Python - Loops Python - List Python - Tuple Python - Set Python - Dictionary Python - Function Python - Module Python - Date & Time Python - Input Output Python - Error & Exception Python - File Handling
Python OOP
OOP - Introduction OOP - Class Members OOP - Constructor Destructor OOP - Data Hiding OOP - Inheritance OOP - Overriding OOP - Overloading

Python Variable

Unlike other programming languages, Python has no command for declaring a variable.

A variable is created the moment you first assign a value to it.

Variables do not need to be declared with any particular type and can even change type after they have been set.

You can also delete the reference to a variable by using the del keyword.


Variable Names

A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). 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)

Remember that variables are case-sensitive


Standard Data Types

The data stored in memory can be of many types. For example, a person's age is stored as a numeric value and his or her address is stored as alphanumeric characters. Python has various standard data types that are used to define the operations possible on them and the storage method for each of them.

Python has five standard data types:

  1. Numbers
  2. String
  3. bool
  4. List
  5. Tuple
  6. Dictionary

Global and Local Variables

Global variables are the one that are defined and declared outside a function and we need to use them inside a function.

We use global keyword inside a function in order to use global variables.

Local variables are the one that are defined and declared inside a function or block

You will learn more about Global and Local Variables later in this tutorial.


Python Keywords

Python has the following keywords or reserved words; they cannot be used as identifiers (variables name).

  • and
  • as
  • assert
  • async
  • await
  • break
  • class
  • continue
  • def
  • del
  • elif
  • else
  • except
  • exec
  • false
  • finally
  • for
  • from
  • global
  • if
  • import
  • in
  • is
  • lambda
  • None
  • nonlocal
  • not
  • or
  • pass
  • print
  • raise
  • return
  • True
  • try
  • while
  • with
  • yield

Note: exec and print are functions, so they are not keywords anymore.