Python Lambda / Anonymous Function

1. What is a Lambda Function

A lambda function is a small anonymous function defined using the lambda keyword. It can have any number of arguments but only one expression.

square = lambda x: x ** 2
print(square(5))  # Output: 25

Lambda functions are used for concise, one-line operations.

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2. Lambda with Multiple Arguments

add = lambda a, b: a + b
print(add(10, 5))  # Output: 15

Supports multiple inputs with a single return expression.

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3. Lambda Without Assignment (Inline Usage)

print((lambda x, y: x * y)(4, 5))  # Output: 20

Lambda can be defined and executed immediately.

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4. Lambda with map()

numbers = [1, 2, 3, 4]

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

Used to apply a function to each item in an iterable.

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5. Lambda with filter()

numbers = [1, 2, 3, 4, 5, 6]

even_numbers = list(filter(lambda x: x % 2 == 0, numbers))
print(even_numbers)  # Output: [2, 4, 6]

Filters elements based on a condition.

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6. Lambda with reduce()

from functools import reduce

numbers = [1, 2, 3, 4]

total = reduce(lambda x, y: x + y, numbers)
print(total)  # Output: 10

Reduces an iterable to a single result.

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7. Lambda for Sorting Key

students = [("Alice", 85), ("Bob", 72), ("Charlie", 90)]

students.sort(key=lambda x: x[1])
print(students)

Lambda is commonly used as a custom sorting key.

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8. Lambda in List Comprehension Context

multipliers = [(lambda x: x * n) for n in range(1, 4)]

print(multipliers)  # Output: 5
print(multipliers)  # Output: 10

Demonstrates functional programming patterns.

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9. Lambda vs Normal Function

def square_func(x):
    return x ** 2

square_lambda = lambda x: x ** 2

print(square_func(4))     # 16
print(square_lambda(4))   # 16

Lambda is more concise but less suitable for complex logic.

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10. Real-World Lambda Example

employees = [
    {"name": "Alice", "salary": 5000},
    {"name": "Bob", "salary": 3000},
    {"name": "Charlie", "salary": 7000}
]

highest_paid = max(employees, key=lambda emp: emp["salary"])
print(highest_paid)

Lambda enables expressive data processing in analytics and business logic.