What is the difference between "lambda" and "def" in Python?

Question

Jayant Kumar · Accepted Answer

Table of Contents
Introduction
In Python, both lambda and def are used to define functions, but they serve different purposes and have distinct syntax and use cases. Understanding the differences between lambda and def is essential for writing clear and effective code. This article explores these differences, including syntax, functionality, and practical applications.
Key Differences Between lambda and def
1. Syntax and Definition

**lambda**: The lambda keyword is used to create small, anonymous functions, often referred to as lambda functions. These functions are defined in a single line of code and are typically used for short-term operations or as arguments to higher-order functions.
**def**: The def keyword is used to create named functions with more extensive functionality. Functions defined with def can contain multiple lines of code, have a name, and can include complex logic, documentation, and default values.

Example:
# Using lambda to create a simple function
add = lambda x, y: x + y
print(add(3, 4))  # Output: 7

# Using def to create a function
def add(x, y):
    return x + y

print(add(3, 4))  # Output: 7

2. Functionality and Use Cases

**lambda**: Lambda functions are generally used for short, throwaway functions that are not needed beyond a single expression. They are often used with functions like map(), filter(), and sorted() where a small function is needed temporarily.
**def**: Functions defined with def are more versatile and can be used for more complex operations. They are suitable for cases where functions need to be reused, involve multiple statements, or require extensive documentation.

Example:
# Using lambda with map
numbers = [1, 2, 3, 4]
squared = map(lambda x: x ** 2, numbers)
print(list(squared))  # Output: [1, 4, 9, 16]

# Using def with map
def square(x):
    return x ** 2

squared = map(square, numbers)
print(list(squared))  # Output: [1, 4, 9, 16]

3. Limitations

**lambda**: Lambda functions are limited to a single expression. They cannot contain multiple expressions, statements, or annotations. They also lack a name and documentation, which can make debugging and readability more challenging.
**def**: Functions defined with def can include multiple statements, complex logic, and support for documentation strings (docstrings). They also allow for better readability, debugging, and reuse.

Example:
# Using lambda for a simple operation
increment = lambda x: x + 1
print(increment(5))  # Output: 6

# Using def for more complex logic
def increment(x):
    """
    Increment the given number by 1.
    """
    return x + 1

print(increment(5))  # Output: 6

Practical Examples
Example : Lambda for Inline Operations
# Using lambda for quick, inline operations
sorted_list = sorted([3, 1, 4, 1, 5], key=lambda x: x % 2)
print(sorted_list)  # Output: [4, 1, 1, 3, 5] (sorted by evenness)

Example : Def for Reusable Functions
# Using def to define a function for repeated use
def multiply(x, y):
    return x * y

result = multiply(6, 7)
print(result)  # Output: 42

Conclusion
In Python, lambda and def serve different purposes for function definition. lambda is used for creating short, anonymous functions suitable for quick, temporary use, while def is used for defining named functions with more extensive functionality, multiple statements, and better documentation. Choosing between lambda and def depends on the complexity of the function and its intended use.

What is the difference between "lambda" and "def" in Python?

Table of Contents

Introduction

Key Differences Between `lambda` and `def`

1. Syntax and Definition

Example:

2. Functionality and Use Cases

Example:

3. Limitations

Example:

Practical Examples

Example : Lambda for Inline Operations

Example : Def for Reusable Functions

Conclusion

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