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06. First-Class Functions

In Python, functions are "first-class citizens," meaning they can be treated like any other object.

Assigning Functions to Variables​

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

say_hello = greet
print(say_hello("Alice"))

Passing Functions as Arguments​

def apply(func, value):
    return func(value)

def square(x): return x*x
print(apply(square, 5))

Returning Functions from Functions​

def make_multiplier(factor):
    def multiply(x):
        return x * factor
    return multiply

double = make_multiplier(2)
print(double(10))  # 20

Practice Challenge​

Write a function make_adder(n) that returns a function which adds n to its input.

Wrap-Up​

  • Functions can be assigned, passed, and returned.
  • This enables higher-order functions and functional programming in Python.