Python Functions

1. Defining a Basic Function

def greet():
    print("Hello, Python!")

greet()

A function is defined using the def keyword followed by the function name and parentheses.

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2. Function with Parameters

def greet_user(name):
    print(f"Hello, {name}!")

greet_user("Alice")

Parameters allow functions to accept external input.

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3. Function with Return Value

def add(a, b):
    return a + b

result = add(5, 3)
print(result)  # Output: 8

The return statement sends a value back to the caller.

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4. Default Parameters

def greet(name="Guest"):
    print(f"Hello, {name}!")

greet()
greet("Bob")

Default values are used when no argument is provided.

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5. Keyword Arguments

def student_info(name, age):
    print(f"Name: {name}, Age: {age}")

student_info(age=20, name="Alice")

Arguments can be passed by name for clarity.

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6. *Variable-Length Arguments (args)

def sum_numbers(*args):
    return sum(args)

print(sum_numbers(1, 2, 3, 4))  # Output: 10

Allows passing multiple positional arguments.

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7. **Keyword Variable-Length Arguments (kwargs)

def display_profile(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")

display_profile(name="Alice", role="Engineer")

Accepts arbitrary keyword arguments.

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8. **Function with Both *args and kwargs

def complete_profile(*args, **kwargs):
    print("Positional:", args)
    print("Keyword:", kwargs)

complete_profile("Python", level="Advanced", year=2025)

Supports flexible function signatures.

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9. Lambda (Anonymous) Functions

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

Used for short, inline function definitions.

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10. Recursive Functions

def factorial(n):
    if n == 0:
        return 1
    return n * factorial(n - 1)

print(factorial(5))  # Output: 120

A function calling itself to solve repetitive problems.

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