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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.

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