What is the difference between "in" and "not in" in Python?

Table of Contents

• Introduction
• Key Differences Between in and not in
  • 1. Purpose and Function
  • Example:
  • 2. Use with Different Data Types
  • Example:
  • 3. Conditional Statements
  • Example:
• Practical Examples
  • Example : Checking Membership in a List
  • Example : Membership Testing with Strings
• Conclusion

Introduction

In Python, the in and not in operators are used for membership testing, which allows you to check if a value exists within a collection such as a list, tuple, or dictionary. These operators are fundamental for conditional statements and data manipulation. This article will detail the differences between in and not in, explaining their usage and providing practical examples to illustrate their application.

Key Differences Between in and not in

1. Purpose and Function

• in: The in operator checks if a specified value is present within a collection. It returns True if the value exists in the collection and False otherwise.
• not in: The not in operator checks if a specified value is not present within a collection. It returns True if the value is not found and False if the value exists in the collection.

Example:

2. Use with Different Data Types

• in: Can be used with various data types, including lists, tuples, strings, sets, and dictionaries. For dictionaries, in checks if a key exists in the dictionary.
• not in: Functions similarly to in, working with lists, tuples, strings, sets, and dictionaries. For dictionaries, it checks if a key does not exist.

Example:

3. Conditional Statements

• in: Commonly used in if statements to perform actions based on the presence of an item in a collection.
• not in: Used to check for the absence of an item and can be employed in if statements to handle cases where a value is missing.

Example:

Practical Examples

Example : Checking Membership in a List

Example : Membership Testing with Strings

Conclusion

The in and not in operators in Python are essential for membership testing in various data structures. in checks for the presence of a value, returning True if the value is found, while not in checks for the absence of a value, returning True if the value is not present. Understanding these operators and their applications helps in writing efficient and effective conditional statements and managing collections in Python.