Unit 3: Functions, Modules, and Packages notes, polytechnic 3rd semester python notes

3.1 Organizing Code Using Functions

Functions are reusable blocks of code designed to perform a specific task. Using functions helps in organizing code, making it more readable and modular.

Syntax:

python

def function_name(parameters):
    # Code block
    return result

Example:

python

def add_numbers(a, b):
    return a + b

result = add_numbers(5, 10)
print(result)  # Output: 15

Functions can take arguments (parameters) and return values. They allow for code reuse and make programs easier to understand and maintain.

• Advantages of Using Functions:
  • Modularity: Functions break large code blocks into smaller, manageable pieces.
  • Reusability: Functions can be reused in different parts of the program.
  • Maintainability: Functions make it easier to debug and maintain code.
  • Abstraction: They allow complex tasks to be abstracted into a simple function call.

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3.2 Organizing Projects into Modules

In Python, a module is a file containing Python code, which can include functions, classes, and variables. Organizing code into modules allows you to split larger programs into smaller, more manageable files.

Creating a Module: To create a module, save the Python code into a .py file.

Example (module: mymath.py):

python

def add(a, b):
    return a + b

def subtract(a, b):
    return a - b

You can then import this module into other Python files using the import statement.

Using the Module:

python

import mymath

result = mymath.add(5, 3)
print(result)  # Output: 8

• Benefits of Modules:
  • Code Organization: Large programs can be split across multiple files.
  • Namespace Management: Variables and functions in different modules won’t interfere with each other.
  • Reusability: Modules can be reused across multiple projects.

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3.3 Importing Own Modules as Well as External Modules

You can import your own modules or use external modules provided by the Python Standard Library or third-party libraries.

• Importing a Module:

  python
  
  import module_name
  

  You can also use specific parts of a module:

  python
  
  from module_name import function_name
  

• Example (Own Module):

  python
  
  # Import the entire module
  import mymodule
  
  # Import specific function
  from mymodule import myfunction
  

• Importing External Modules: Python comes with a vast collection of modules in the Standard Library. You can also install third-party modules using pip (Python’s package manager).

  Example (External Module: math):

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

• Example (Installing and Importing Third-Party Module):

  bash
  
  pip install requests
  

  Usage:

  python
  
  import requests
  response = requests.get("https://example.com")
  print(response.status_code)
  

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3.4 Understanding Packages

A package in Python is a way of organizing related modules into a directory hierarchy. A package contains an __init__.py file to distinguish it as a package and can contain sub-packages or modules.

Creating a Package:

1. Create a directory for the package.
2. Add an __init__.py file (can be empty).
3. Place modules inside the directory.

Example:

markdown

mypackage/
    __init__.py
    module1.py
    module2.py

Importing from a Package:

python

from mypackage import module1

Packages allow for a structured way to organize complex projects into a hierarchy of modules, making code modular and scalable.

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Summary:

• Functions help organize reusable code into blocks that can perform specific tasks.
• Modules organize code into separate files that can be imported, improving the structure and readability of a project.
• Packages group related modules into a directory structure, facilitating better project organization.