Modules and Libraries in Python

Learn Python variables with this beginner-friendly guide. Understand variable naming rules, assignments, and operations with examples and exercises. Perfect for students and professionals starting their Python journey.

Modules and Libraries in Python

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.