Introduction to Functions
Functions are reusable blocks of code that perform a specific task. They help organize code into manageable sections and promote code reuse.
def greet(name):
print(f"Hello, {name}!")
# Call the function
greet("Alice") # Output: Hello, Alice!
Defining Functions
Functions in Python are defined using the def keyword followed by the function name and parentheses.
# Basic function definition
def function_name(parameters):
"""docstring""" # Optional documentation
# function body
return # optional return value
Parameters and Arguments
Functions can accept parameters (variables listed in the function definition) and arguments (values passed to the function when called).
# Function with parameters
def add_numbers(a, b):
return a + b
# Calling with arguments
result = add_numbers(5, 3)
print(result) # Output: 8
# Default parameter values
def greet(name="Guest"):
print(f"Hello, {name}")
greet() # Output: Hello, Guest
greet("Alice") # Output: Hello, Alice
Return Values
Functions can return values using the return statement. A function can return multiple values as a tuple.
# Function with return value
def square(number):
return number ** 2
squared = square(4)
print(squared) # Output: 16
# Returning multiple values
def min_max(numbers):
return min(numbers), max(numbers)
min_val, max_val = min_max([5, 2, 9, 1])
print(f"Min: {min_val}, Max: {max_val}") # Output: Min: 1, Max: 9
Variable Scope
Variables defined inside a function are local to that function. Global variables can be accessed but need the global keyword to be modified.
# Global vs local scope
global_var = "I'm global"
def scope_demo():
local_var = "I'm local"
print(global_var) # Access global variable
print(local_var) # Access local variable
scope_demo()
print(global_var) # Works
# print(local_var) # Would cause an error
Lambda Functions
Lambda functions are small anonymous functions defined with the lambda keyword.
# Regular function
def square(x):
return x * x
# Equivalent lambda function
square = lambda x: x * x
print(square(5)) # Output: 25
# Using lambda with built-in functions
numbers = [1, 2, 3, 4]
squared = list(map(lambda x: x**2, numbers))
print(squared) # Output: [1, 4, 9, 16]
Python Function Videos
Master Python functions with these handpicked YouTube tutorials:
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