Python Lambda Function Explained with Examples – Simple Guide for learners

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Python Lambda Function Explained – Easy Guide for Students & Professionals

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Lambda functions in Python are small, powerful, and often misunderstood — but once you get the hang of them, they become a valuable tool in your coding toolkit.

In this guide, we’ll explain what lambda functions are, when to use them, how to write them, and some real-world examples. Whether you’re a beginner or a working professional, this article will help you master Python’s anonymous functions.


What is a Lambda Function in Python?

A lambda function is a small, anonymous function defined using the keyword lambda.

It is:

  • Used for short, one-line functions
  • Often used where a function is needed temporarily
  • Can take any number of arguments but has only one expression

Syntax of Lambda Function

lambda arguments: expression

This returns a function object that you can call just like a normal function.


Basic Example

Let’s write a lambda function that adds 10 to a number:

add_ten = lambda x: x + 10
print(add_ten(5))  # Output: 15

Here, lambda x: x + 10 is equivalent to:

def add_ten(x):
    return x + 10

🔁 Multiple Arguments Example

multiply = lambda x, y: x * y
print(multiply(3, 4))  # Output: 12

Where to Use Lambda Functions

Lambda functions are most commonly used:

  • Inside map(), filter(), and reduce()
  • When passing a simple function as an argument
  • To simplify short logic without cluttering the code

Lambda with map()

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

Lambda with filter()

nums = [1, 2, 3, 4, 5, 6]
evens = list(filter(lambda x: x % 2 == 0, nums))
print(evens)  # Output: [2, 4, 6]

Lambda with sorted()

students = [('Alice', 85), ('Bob', 72), ('Charlie', 90)]
# Sort by score (second element)
sorted_students = sorted(students, key=lambda x: x[1])
print(sorted_students)
# Output: [('Bob', 72), ('Alice', 85), ('Charlie', 90)]

⚠️ When NOT to Use Lambda

  • For complex logic (use def instead)
  • When readability is more important than brevity
  • If the function needs a docstring or name

📝 Summary Table

Feature Lambda Function Normal Function (def)
Syntax One-liner Multi-line allowed
Naming Anonymous Named
Usage Quick, temporary functions Reusable and readable
Supports Docstring ❌ ✅
Used with map(), filter(), sort(), etc. Anywhere

Practice Task for Students

Try writing a lambda function that checks if a number is even or odd:

is_even = lambda x: "Even" if x % 2 == 0 else "Odd"
print(is_even(7))  # Output: Odd

Real-World Use Case: Sorting Dictionary by Value

data = {'a': 5, 'b': 2, 'c': 9}
sorted_data = sorted(data.items(), key=lambda item: item[1])
print(sorted_data)  # Output: [('b', 2), ('a', 5), ('c', 9)]

Conclusion

Lambda functions are an elegant way to write quick, throwaway functions without creating full function definitions. For students, they help understand functional programming. For professionals, they help write cleaner, faster, and more Pythonic code.

When used wisely, lambda functions can improve your code efficiency — just remember to keep them short and readable!


watch video to understand Python Lambda Function below: 

 

 
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