Python Function Examples

Just getting started with Python? This page is packed with simple, beginner-friendly function examples that help you build a strong foundation.
Functions are reusable blocks of code. On this page, you'll explore how to define and use def functions, pass arguments, use return values, and work with special cases like *args, **kwargs, and lambdas.

1. Basic function definition and call
python
# Example 1: Basic function
def greet():
    print("Hello from a function")

greet()
2. Function with parameters
python
# Example 2: Function with parameters
def greet(name):
    print(f"Hello, {name}!")

greet("Alice")
3. Function with return value
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# Example 3: Return value
def add(a, b):
    return a + b

result = add(3, 5)
print("Sum is:", result)
4. Default parameter values
python
# Example 4: Default parameters
def greet(name="Guest"):
    print(f"Welcome, {name}")

greet()
greet("Eve")
5. Keyword arguments
python
# Example 5: Keyword arguments
def describe_pet(animal, name):
    print(f"I have a {animal} named {name}")

describe_pet(name="Tommy", animal="dog")
6. Variable number of arguments
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# Example 6: *args
def print_numbers(*nums):
    for num in nums:
        print(num)

print_numbers(1, 2, 3, 4)
7. Function with **kwargs
python
# Example 7: **kwargs
def print_info(**info):
    for key, value in info.items():
        print(f"{key}: {value}")

print_info(name="Alice", age=25)
8. Recursive function
python
# Example 8: Recursion
def factorial(n):
    if n == 1:
        return 1
    return n * factorial(n - 1)

print(factorial(5))
9. Lambda function
python
# Example 9: Lambda
square = lambda x: x * x
print(square(6))
10. Function with type hints
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# Example 10: Type hints
def multiply(x: int, y: int) -> int:
    return x * y

print(multiply(4, 5))
11. Function to check even or odd
python
# Example 11: Check even or odd
def check_even_odd(num):
    if num % 2 == 0:
        print(f"{num} is even")
    else:
        print(f"{num} is odd")

check_even_odd(7)
12. Function to reverse a string
python
# Example 12: Reverse a string
def reverse_string(s):
    return s[::-1]

print(reverse_string("hello"))
13. Function to calculate average of a list
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# Example 13: Average of numbers
def average(numbers):
    return sum(numbers) / len(numbers)

print(average([10, 20, 30]))
14. Function with nested function
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# Example 14: Nested function
def outer():
    def inner():
        print("Hello from inner function")
    inner()

outer()
15. Global vs local variable
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# Example 15: Scope example
x = 10

def change():
    x = 5  # local variable
    print("Inside function:", x)

change()
print("Outside function:", x)
16. Function to check prime number
python
# Example 16: Prime check
def is_prime(n):
    if n < 2:
        return False
    for i in range(2, int(n**0.5)+1):
        if n % i == 0:
            return False
    return True

print(is_prime(11))
17. Function to count vowels in a string
python
# Example 17: Count vowels
def count_vowels(s):
    vowels = "aeiou"
    return sum(1 for char in s.lower() if char in vowels)

print(count_vowels("Python"))
18. Function that returns multiple values
python
# Example 18: Multiple return values
def min_max(numbers):
    return min(numbers), max(numbers)

low, high = min_max([3, 1, 8, 4])
print("Min:", low, "Max:", high)
19. Higher-order function (function as argument)
python
# Example 19: Function as argument
def apply_twice(func, value):
    return func(func(value))

def increment(x):
    return x + 1

print(apply_twice(increment, 3))
20. Function with docstring
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# Example 20: Docstring
def square(n):
    """Return the square of a number."""
    return n * n

print(square(6))
print(square.__doc__)
21. Function to convert Celsius to Fahrenheit
python
# Example 21: Celsius to Fahrenheit
def celsius_to_fahrenheit(c):
    return (c * 9/5) + 32

print(celsius_to_fahrenheit(25))
22. Function to find the longest word in a list
python
# Example 22: Longest word
def longest_word(words):
    return max(words, key=len)

print(longest_word(["python", "java", "golang", "rust"]))
23. Function to check if a string is a palindrome
python
# Example 23: Palindrome check
def is_palindrome(s):
    return s == s[::-1]

print(is_palindrome("madam"))
24. Function to get factorial using recursion
python
# Example 24: Recursive factorial
def factorial(n):
    if n == 0:
        return 1
    return n * factorial(n - 1)

print(factorial(5))
25. Function to flatten a 2D list
python
# Example 25: Flatten list
def flatten(matrix):
    return [item for row in matrix for item in row]

print(flatten([[1, 2], [3, 4], [5, 6]]))
26. Function to remove duplicates from a list
python
# Example 26: Remove duplicates
def remove_duplicates(lst):
    return list(set(lst))

print(remove_duplicates([1, 2, 2, 3, 4, 4, 5]))
27. Function with try-except block
python
# Example 27: Try-except in function
def divide(a, b):
    try:
        return a / b
    except ZeroDivisionError:
        return "Cannot divide by zero"

print(divide(10, 0))
28. Function to capitalize each word
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# Example 28: Capitalize words
def title_case(sentence):
    return sentence.title()

print(title_case("hello world from python"))
29. Function to count word frequency
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# Example 29: Word count
def word_count(text):
    words = text.split()
    freq = {}
    for word in words:
        freq[word] = freq.get(word, 0) + 1
    return freq

print(word_count("apple orange apple banana orange apple"))
30. Function to generate Fibonacci sequence
python
# Example 30: Fibonacci sequence
def fibonacci(n):
    sequence = [0, 1]
    for _ in range(2, n):
        sequence.append(sequence[-1] + sequence[-2])
    return sequence[:n]

print(fibonacci(10))
31. Function to check if a number is positive, negative or zero
python
# Example 31: Number sign check
def check_number(n):
    if n > 0:
        return "Positive"
    elif n < 0:
        return "Negative"
    else:
        return "Zero"

print(check_number(-5))
32. Function to count characters in a string
python
# Example 32: Character count
def char_count(s):
    return {char: s.count(char) for char in set(s)}

print(char_count("hello"))
33. Function to check if a list is sorted
python
# Example 33: Sorted check
def is_sorted(lst):
    return lst == sorted(lst)

print(is_sorted([1, 2, 3]))
print(is_sorted([3, 2, 1]))
34. Function to find common elements in two lists
python
# Example 34: Common elements
def common_elements(a, b):
    return list(set(a) & set(b))

print(common_elements([1, 2, 3], [2, 3, 4]))
35. Function to repeat a string multiple times
python
# Example 35: Repeat string
def repeat_string(s, n):
    return s * n

print(repeat_string("ha", 3))
36. Function to convert a list of strings to uppercase
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# Example 36: Uppercase list
def to_uppercase(words):
    return [word.upper() for word in words]

print(to_uppercase(["python", "code", "fun"]))
37. Function to get the second largest number in a list
python
# Example 37: Second largest
def second_largest(numbers):
    unique = list(set(numbers))
    unique.sort()
    return unique[-2] if len(unique) >= 2 else None

print(second_largest([10, 20, 30, 30]))
38. Function to format full name
python
# Example 38: Format name
def format_name(first, last):
    return f"{first.strip().title()} {last.strip().title()}"

print(format_name("  john", "DOE "))
39. Function to calculate the area of a circle
python
# Example 39: Circle area
import math

def circle_area(radius):
    return math.pi * radius ** 2

print(circle_area(3))
40. Function to filter even numbers from a list
python
# Example 40: Filter even numbers
def filter_even(nums):
    return [n for n in nums if n % 2 == 0]

print(filter_even([1, 2, 3, 4, 5, 6]))

What’s Next?

Awesome work learning how Python functions work! Now that you understand the basics, it's time to take your skills to the next level with powerful tools like iterators, generators, closures, and decorators. These concepts will help you write more efficient, flexible, and Pythonic code.