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Learn/Python/Foundations

Python•Foundations

Python None

Overview

None is a special constant in Python that represents the absence of a value.

Its data type is

NoneType, and

None is the only instance of a

NoneType object.

NoneType

Variables can be assigned

None to indicate "no value" or "not set".

Example

Assign and display a

None value:

x = None print(x)

Use type()

to see the type of a None value.

Example

Assign and print the data type of a

None value:

x = None print(type(x))

Comparing to None

To compare a value to

None, use the identity operator is or is not

Example

Use the identity operator is for comparisons with

None

Formula

result = None if result is None:

print("No result yet")
else:
print("Result is ready")

Example

Similar example, but using is not instead:

Formula

result = None if result is not None:

print("Result is ready")
else:
print("No result yet")

True or False

None evaluates to

False in a boolean context.

Example

Check truthiness:

print(bool(None))

Functions returning None

Functions that do not explicitly return a value return None by default.

Example

A function without a return statement returns

None

def myfunc():

Formula

x = 5 x = myfunc()

print(x)

Loading lesson path

Learn/Python/Foundations

Python•Foundations

Python None

Overview

None is a special constant in Python that represents the absence of a value.

Its data type is

NoneType, and

None is the only instance of a

NoneType object.

NoneType

Variables can be assigned

None to indicate "no value" or "not set".

Example

Assign and display a

None value:

x = None print(x)

Use type()

to see the type of a None value.

Example

Assign and print the data type of a

None value:

x = None print(type(x))

Comparing to None

To compare a value to

None, use the identity operator is or is not

Example

Use the identity operator is for comparisons with

None

Formula

result = None if result is None:

print("No result yet")
else:
print("Result is ready")

Example

Similar example, but using is not instead:

Formula

result = None if result is not None:

print("Result is ready")
else:
print("No result yet")

True or False

None evaluates to

False in a boolean context.

Example

Check truthiness:

print(bool(None))

Functions returning None

Functions that do not explicitly return a value return None by default.

Example

A function without a return statement returns

None

def myfunc():

Formula

x = 5 x = myfunc()

print(x)