Python Function Examples

Below are some Python function examples along with their solutions, descriptions, and unique features that each implementation teaches.

Example 1: Factorial of a Number

Question: Write a Python script named factorial.py that asks the user for a number and prints the factorial of that number.

def factorial(n):
    result = 1
    for i in range(2, n + 1):
        result *= i
    return result

number = int(input("Enter a number: "))
print(f"Factorial of {number} is {factorial(number)}")

Output:

C:\> python factorial.py
Enter a number: 5
Factorial of 5 is 120
C:\>

Description: The factorial(n) function multiplies all the numbers from 1 to n to calculate the factorial. The program then takes user input, calls the function, and prints the factorial of the number.

Unique Feature: This implementation demonstrates the use of a for loop to iterate from 2 to n, which is efficient and easy to understand. It highlights the importance of iterative multiplication in calculating factorials.

Example 2: Find the Largest Number in a List

Question: Create a Python script named find_largest.py that takes a list of numbers as input and prints the largest number in the list.

def find_largest(numbers):
    largest = numbers[0]
    for number in numbers:
        if number > largest:
            largest = number
    return largest

numbers = list(map(int, input("Enter numbers separated by space: ").split()))
print(f"The largest number is {find_largest(numbers)}")

Output:

C:\> python find_largest.py
Enter numbers separated by space: 10 20 30 5
The largest number is 30
C:\>

Description: The find_largest(numbers) function iterates through a list and compares each number to find the largest one. The program asks the user for a list of numbers, calls the function, and prints the largest number.

Unique Feature: This implementation teaches how to use comparison within a loop to determine the maximum value in a list. It also introduces list input handling using map() and split().

Example 3: Convert Celsius to Fahrenheit

Question: Write a Python script named celsius_to_fahrenheit.py that converts a temperature from Celsius to Fahrenheit.

def celsius_to_fahrenheit(celsius):
    return (celsius * 9/5) + 32

celsius = float(input("Enter temperature in Celsius: "))
print(f"{celsius}°C is equal to {celsius_to_fahrenheit(celsius)}°F")

Output:

C:\> python celsius_to_fahrenheit.py
Enter temperature in Celsius: 25
25.0°C is equal to 77.0°F
C:\>

Description: The celsius_to_fahrenheit(celsius) function applies the formula (celsius * 9/5) + 32 to convert the temperature. The program gets the Celsius value from the user, converts it, and prints the Fahrenheit equivalent.

Unique Feature: This example emphasizes the simplicity and importance of using arithmetic operations within functions to perform conversions.

Example 4: Calculate the Area of a Circle

Question: Create a Python script named area_of_circle.py that calculates the area of a circle given its radius.

import math

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

radius = float(input("Enter the radius of the circle: "))
print(f"The area of the circle is {area_of_circle(radius)}")

Output:

C:\> python area_of_circle.py
Enter the radius of the circle: 5
The area of the circle is 78.53981633974483
C:\>

Description: The area_of_circle(radius) function calculates the area using the formula πr² where π is accessed from the math module. The user inputs the radius, and the program calculates and prints the area.

Unique Feature: This implementation highlights the use of the math module for accessing mathematical constants like π. It also demonstrates the power of Python's built-in libraries for performing common mathematical operations.

Example 5: Sum of First N Natural Numbers

Question: Write a Python script named sum_of_n_numbers.py that calculates the sum of the first n natural numbers.

def sum_of_n_numbers(n):
    return n * (n + 1) // 2

n = int(input("Enter a number: "))
print(f"The sum of the first {n} natural numbers is {sum_of_n_numbers(n)}")

Output:

C:\> python sum_of_n_numbers.py
Enter a number: 10
The sum of the first 10 natural numbers is 55
C:\>

Description: The sum_of_n_numbers(n) function calculates the sum using the formula n * (n + 1) // 2. The user provides a number n, and the program prints the sum of the first n natural numbers.

Unique Feature: This example introduces the formula for the sum of an arithmetic series and shows how such formulas can simplify code and improve efficiency compared to iterative summation.

Example 6: Check if a Number is Prime

Question: Create a Python script named is_prime.py that checks whether a given number is prime or not.

import math

def is_prime(n):
    if n <= 1:
        return False
    for i in range(2, int(math.sqrt(n)) + 1):
        if n % i == 0:
            return False
    return True

number = int(input("Enter a number: "))
print(f"{number} is {'a prime number' if is_prime(number) else 'not a prime number'}")

Output:

C:\> python is_prime.py
Enter a number: 17
17 is a prime number
C:\>

Description: The is_prime(n) function checks if the number has any divisors other than 1 and itself by iterating up to the square root of n. The program then informs the user if the number is prime or not.

Unique Feature: This implementation teaches an optimized approach to checking for primality by reducing the number of iterations required, leveraging the mathematical property that a larger factor of a number must be greater than its square root.

Example 7: Reverse a String

Question: Write a Python script named reverse_string.py that takes a string as input and prints the reversed string.

def reverse_string(s):
    return s[::-1]

string = input("Enter a string: ")
print(f"Reversed string is {reverse_string(string)}")

Output:

C:\> python reverse_string.py
Enter a string: Python
Reversed string is nohtyP
C:\>

Description: The reverse_string(s) function uses slicing to reverse the input string. The program takes a string from the user and prints its reversed form.

Unique Feature: This example demonstrates the use of Python's powerful slicing feature to manipulate sequences efficiently, emphasizing the simplicity and readability of Python code.

Example 8: Find the GCD of Two Numbers

Question: Create a Python script named gcd.py that calculates the greatest common divisor (GCD) of two numbers.

def gcd(a, b):
    while b:
        a, b = b, a % b
    return a

a = int(input("Enter the first number: "))
b = int(input("Enter the second number: "))
print(f"The GCD of {a} and {b} is {gcd(a, b)}")

Output:

C:\> python gcd.py
Enter the first number: 48
Enter the second number: 18
The GCD of 48 and 18 is 6
C:\>

Description: The gcd(a, b) function uses the Euclidean algorithm to find the GCD. The program prompts the user for two numbers and prints their GCD.

Unique Feature: This example illustrates the use of the Euclidean algorithm for efficiently finding the GCD, highlighting how swapping and modulo operations can be combined to solve mathematical problems.

Example 9: Calculate the Sum of a List of Numbers

Question: Write a Python script named sum_of_list.py that takes a list of numbers and calculates their sum.

def sum_of_list(numbers):
    total = 0
    for number in numbers:
        total += number
    return total

numbers = list(map(int, input("Enter numbers separated by space: ").split()))
print(f"The sum of the numbers is {sum_of_list(numbers)}")

Output:

C:\> python sum_of_list.py
Enter numbers separated by space: 1 2 3 4 5
The sum of the numbers is 15
C:\>

Description: The sum_of_list(numbers) function iterates through the list, adding each element to calculate the total sum. The program then displays the sum to the user.

Unique Feature: This implementation reinforces the concept of iteration and accumulation within a loop, demonstrating a fundamental pattern in programming for summing values.

Example 10: Calculate the Square of a Number

Question: Create a Python script named square.py that calculates the square of a given number.

def square(n):
    return n ** 2

number = int(input("Enter a number: "))
print(f"The square of {number} is {square(number)}")

Output:

C:\> python square.py
Enter a number: 7
The square of 7 is 49
C:\>

Description: The square(n) function simply returns n ** 2, the square of the input number. The user provides a number, and the program outputs its square.

Unique Feature: This example highlights the use of Python's exponentiation operator ** for performing power calculations, emphasizing the simplicity and expressiveness of the language.