Functions and Modules

What are Functions?

• Functions are reusable blocks of code that perform specific tasks. Instead of writing the same code repeatedly, write it once in a function!
• Think of functions as mini-programs within your program.

Creating Functions

• “`python
• def greet(name):
• print(f'Hello, {name}!')
• greet('Ahmed') # Prints: Hello, Ahmed!
• greet('Sara') # Prints: Hello, Sara!
• “`
• With Return Value:
• “`python
• def add_numbers(a, b):
• return a + b
• result = add_numbers(10, 20)
• print(result) # Prints: 30
• “`

Function Parameters

• Required Parameters:
• `def calculate_tax(amount):`
• Optional Parameters (with default values):
• “`python
• def greet(name, greeting='Hello'):
• print(f'{greeting}, {name}!')
• greet('Ali') # Uses default: Hello, Ali!
• greet('Sara', 'Hi') # Uses custom: Hi, Sara!
• “`

Using Built-in Modules

• Python comes with many pre-built modules (libraries) you can use:
• Math Module:
• “`python
• import math
• print(math.sqrt(16)) # Square root: 4.0
• print(math.pi) # 3.14159…
• “`
• Random Module:
• “`python
• import random
• print(random.randint(1, 100)) # Random number between 1-100
• “`
• Datetime Module:
• “`python
• import datetime
• print(datetime.datetime.now()) # Current date and time
• “`

Real Example: Temperature Converter

• “`python
• def celsius_to_fahrenheit(celsius):
• return (celsius * 9/5) + 32
• def fahrenheit_to_celsius(fahrenheit):
• return (fahrenheit – 32) * 5/9
• temp_c = 25
• temp_f = celsius_to_fahrenheit(temp_c)
• print(f'{temp_c}°C = {temp_f}°F')
• “`