Functions & Lambdas

Functions are a way to bundle a set of instructions that you want to use repeatedly. They make your code modular, readable, and easier to debug.

1. Defining a Function

Use the def keyword followed by the function name and parentheses.

def greet(name):
    return f"Hello, {name}!"

message = greet("Pradeep")
print(message)

2. Dynamic Arguments

• Default Arguments: Provide a fallback value.
• *args: Receive a variable number of positional arguments (as a tuple).
• **kwargs: Receive a variable number of keyword arguments (as a dictionary).

def add_all(*numbers):
    return sum(numbers)

print(add_all(1, 2, 3, 4)) # 10

3. Lambda Expressions

Lambdas are small, anonymous functions that can have any number of arguments but only one expression. They are often used with map() and filter().

# Standard: sum = lambda a, b : a + b
square = lambda x : x * x
print(square(5)) # 25

# Used in sorting
pairs = [(1, 'one'), (2, 'two'), (3, 'three')]
pairs.sort(key=lambda pair: pair[1])