A lambda function is a small anonymous function in Python.

It can have any number of arguments, but only one expression.

✅ Syntax:

lambda arguments: expression

🔹 Key Characteristics

🔸 Basic Example

square = lambda x: x * x
print(square(5))  # Output: 25

This is equivalent to:

def square(x):
    return x * x

🔸 Lambda with Multiple Arguments

add = lambda a, b: a + b
print(add(3, 7))   # Output: 10

🔸 Lambda Inside map()

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

🔸 Lambda Inside filter()

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

🔸 Lambda Inside sorted() with Custom Key

names = ['Abhi', 'John', 'Zack', 'Mark']
sorted_names = sorted(names, key=lambda x: x[-1])
print(sorted_names)
# Output: ['Zack', 'Mark', 'Abhi', 'John']

🔸 Lambda Inside reduce() (from functools)

from functools import reduce

product = reduce(lambda x, y: x * y, [1, 2, 3, 4])
print(product)  # Output: 24

💡 Best Practices

❗ When not to use Lambda?

• When the function logic is complex or multi-line

• When you need reusability or documentation (docstrings)

• When you need clarity (named functions are easier to debug)