Modules and Libraries in Python

Let’s practice using some of the concepts we’ve covered, including modules, functions, and working with external libraries.

Let’s now explore modules and libraries in Python, which are essential for organizing and reusing code, as well as leveraging pre-built functionality.

1. Importing Modules

• Python comes with a standard library of modules, but you can also install third-party libraries using tools like pip.

• You can import a module or specific functions from it using the import keyword.

• Importing a whole module:

  import math
  print(math.sqrt(16))  # Output: 4.0
  

• Importing specific functions:

  from math import sqrt
  print(sqrt(16))  # Output: 4.0
  

• Alias for modules: Sometimes you might want to give a module a shorter name using as:

  import numpy as np
  print(np.array([1, 2, 3]))
  

2. Standard Library

Python comes with many useful built-in modules. Some commonly used ones include:

• math: Provides mathematical functions like sqrt(), pow(), and constants like pi.
• datetime: Useful for handling date and time operations.
• random: For generating random numbers.
• os: For interacting with the operating system (e.g., file manipulation).

Example with random:

   import random
   print(random.randint(1, 10))  # Random integer between 1 and 10

3. Installing External Libraries

To install third-party libraries, you can use pip. For example, to install the popular requests library:

   pip install requests

Once installed, you can import it and use it in your code:

   import requests
   response = requests.get('https://www.example.com')
   print(response.text)

4. Creating Your Own Modules

You can organize your code into modules by saving your functions or classes in separate Python files. For example, if you have a file mymodule.py:

   # mymodule.py
   def greet(name):
       return f"Hello, {name}!"

You can import and use the module like this:

   import mymodule
   print(mymodule.greet("Alice"))

Exercise 1: Using the math module

1. Objective: Use the math module to calculate the area of a circle. The formula is Area = π * r², where r is the radius.
2. Steps:
   • Import the math module.
   • Define a function calculate_area(radius) that returns the area of the circle.
   • Use the function with different radius values and print the result.

Exercise 2: Working with the random module

1. Objective: Write a program that simulates rolling a six-sided die 5 times and prints the results.
2. Steps:
   • Import the random module.
   • Use the randint() function to simulate the die rolls.
   • Print the results of each roll.

Exercise 3: Creating your own module

1. Objective: Create a module that contains a function to check if a number is prime.
2. Steps:
   • Create a Python file named mymodule.py.
   • In this file, define a function is_prime(n) that returns True if the number is prime and False otherwise.
   • In your main script, import the module and test the is_prime() function with a few numbers.