Membership Operators in Python

Membership operators are used to test whether a value or variable is found in a sequence (like a list, tuple, string, or dictionary). There are two membership operators in Python: in and not in.

List of Membership Operators

Examples of Membership Operators

1. Using the in Operator

The in operator checks if a value exists in a sequence.

# Example with a list
fruits = ['apple', 'banana', 'cherry']
print('banana' in fruits)  # Output: True
print('grape' in fruits)   # Output: False

# Example with a string
text = "Hello, world!"
print('Hello' in text)     # Output: True
print('hello' in text)     # Output: False (case-sensitive)

2. Using the not in Operator

The not in operator checks if a value does not exist in a sequence.

# Example with a list
fruits = ['apple', 'banana', 'cherry']
print('grape' not in fruits)  # Output: True
print('banana' not in fruits)  # Output: False

# Example with a string
text = "Hello, world!"
print('earth' not in text)     # Output: True
print('world' not in text)     # Output: False

Examples with Other Data Types

1. Using Membership Operators with Tuples

numbers = (1, 2, 3, 4, 5)
print(3 in numbers)        # Output: True
print(6 not in numbers)    # Output: True

2. Using Membership Operators with Dictionaries

When using in with dictionaries, it checks for the presence of keys.

my_dict = {'name': 'Alice', 'age': 25}
print('name' in my_dict)   # Output: True (key exists)
print('Alice' in my_dict)   # Output: False (value is not checked)

Summary of Membership Operators:

• in: Returns True if the specified value is found in the sequence (list, tuple, string, or dictionary).
• not in: Returns True if the specified value is not found in the sequence.

Membership operators are very useful for quickly checking for the existence of elements within various data structures, making them essential tools for efficient coding in Python.