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Python – Variables

Python Variables and Assignment

A variable is a name, which represents a value. To understand it, open a Python terminal and run below command.

id = 10

You will not see any result on screen. Then what happens here? This is an assignment statement, where id is a variable and 10 is the value assigned to the variable.

A single equal (=) is an assignment operator. Where left side of the operator is the variable and right side operator is a value.

Once a value is assigned to the variable, we can use variable name anywhere in a python program instead of using value.

Variable Names in Python

Similar to other programming languages, Python also have limitations on defining variable names:

  • A variable name must start with a letter or the underscore.
  • A variable name cannot start with a number.
  • A variable name can have a single character or string up to 79 characters.
  • A variable name contains only alpha-numeric characters and underscores (Like: A-Z, a-z, 0-9, and _ ).
  • A Variable names are case-sensitive (id, Id and ID are different variables in Python).

Variable Assignment Examples

Below is the some valid python variable names”

_id = 10
name = "rahul"
name = 'rahul' 
address_1 = "123/3 my address"

You can also assign the same value to multiple variables in single command.

a = b = c = "green"

Also you can assingle multiple values to multiple variables in a single command.

a, b, c = "green", "yellow", "blue"

Local vs Global Variable

A local variable is defined in a function block. It is accessible within the function only. Once the function execution completed, the variable is destroyed.

A Global variable is variable defined in Python program. It is not defined in any function block. It is accessible to entire Python program including functions. A Global variable destroyed only once the script execution completed.

Below is a sample program to show you difference between local and global variables. Here “a” is a global variable and “b” is a local variable of function myfun().

a = "Rahul"

def myfun():
  b = "TecAdmin"
  print(a)
  print(b)

myfun()

print(a)
print(b)  ## You will get error -  'b' is not defined
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