What is "not in" operator in Python?

In Python, the not in membership operator evaluates to True if it does not find a variable in the specified sequence and False otherwise.

Syntax

element not in sequence

Example with Lists

Let's check if elements are not present in a list ?

a = 10
b = 4
numbers = [1, 2, 3, 4, 5]

print(a not in numbers)
print(b not in numbers)

True
False

Since a (10) doesn't belong to numbers, a not in numbers returns True. However, b (4) can be found in numbers, hence b not in numbers returns False.

Example with Strings

The not in operator also works with strings to check for substrings ?

text = "Hello World"

print("Python" not in text)
print("Hello" not in text)
print("xyz" not in text)

True
False
True

Example with Tuples and Sets

You can use not in with any iterable sequence ?

colors_tuple = ("red", "green", "blue")
colors_set = {"red", "green", "blue"}

print("yellow" not in colors_tuple)
print("red" not in colors_set)
print("purple" not in colors_set)

True
False
True

Comparison with 'in' Operator

Conclusion

The not in operator is the logical opposite of in, returning True when an element is absent from a sequence. It works with lists, strings, tuples, sets, and other iterable objects.