Home » Python

Python None Keyword

By IncludeHelp Last updated : December 07, 2024

Description and Usage

Note: None is not a keyword – we are just considering & writing it as a keyword which is a replacement of null (in C/C++).

"None" (case-sensitive) is an object of its own datatype, the NoneType, which is similar to null, it is used to define a null value to the variable or represents that a variable does not have any value at all.

None is a type of <class 'NoneType'>.

Syntax

None

Sample Input/Output

Input:
a = None
print("a: ", a);

Output:
a: None

Example 1

Python code to demonstrate example of None keyword.

# python code to demonstrate example of 
# None keyword

# type of None
print("type of None: ", type(None))

# declaring a variable and initialize it with None
a = None
# printing value
print("a: ", a)

# checkng None in condition
if a == None:
    print("variable \'a\' contains None")
else:
    print("variable \'a\' does not contain None")

# assigning a value and rechecking the condition
a = 100
if a == None:
    print("variable \'a\' contains None")
else:
    print("variable \'a\' does not contain None")

Output

type of None:  <class 'NoneType'>
a:  None
variable 'a' contains None
variable 'a' does not contain None

Example 2: Assigning None to a Variable

x = None
print(x)  # Output: None

Output

None

Example 3: Default Value in Functions

def greet(name=None):
    if name is None:
        print("Hello, Guest!")
    else:
        print(f"Hello, {name}!")

greet()         # Output: Hello, Guest!
greet("Alex")  # Output: Hello, Alice!

Output

Hello, Guest!
Hello, Alex!

Example 4: Checking for None

x = None

if x is None:
    print("x has no value.")
else:
    print("x has a value.")

Output

x has no value.