python-doc/Docs/Basic/06-pkg-modules.md

06 – Packages and Modules in Python

This document explains how modules, packages, and the __name__ concept work in Python. These features help organize code, reuse functionality, and build scalable projects.

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1. Importing External Modules

Python allows you to import external libraries installed in your environment.

Example: Using the emoji Module

Code

import emoji
print(emoji.emojize("abbas is :red_heart:"))

Explanation

• import emoji imports the entire emoji module.
• emoji.emojize() converts emoji aliases into actual emoji characters.
• You must use the module name (emoji) to access its functions.

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Importing a Specific Function

Code

from emoji import emojize
print(emojize("abbas is :red_heart:"))

Explanation

• from emoji import emojize imports only the emojize function.
• You can call the function directly without prefixing the module name.
• This approach is cleaner when you only need a specific function.

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2. Creating a Module

A module is a single Python file containing functions, classes, or variables.

File Structure

hi.py
main.py

hi.py

def hi():
    print("Hi :)")

main.py

import hi
hi.hi()

Explanation

• hi.py is a module.
• hi() is a function defined inside the module.
• import hi loads the module.
• hi.hi() calls the function from the module.

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3. Creating a Package

A package is a directory that contains multiple modules.

Package Structure

honor/
│── __init__.py
│── hi.py
main.py

honor/hi.py

def hello():
    print("Hi :)")

honor/__init__.py

Explanation

• The honor directory is a package.
• __init__.py tells Python that this directory is a package.
• The file can be empty, but it must exist (especially for older Python versions and clarity).

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Importing from a Package (Method 1)

main.py

from honor import hi
hi.hello()

Explanation

• Imports the hi module from the honor package.
• Accesses the function using hi.hello().

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Importing from a Package (Method 2)

main.py

from honor.hi import hello
hello()

Explanation

• Imports the hello function directly.
• Allows calling the function without the module name.
• Cleaner when only one function is needed.

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4. The __name__ Concept

Every Python file has a built-in variable called __name__.

Code

print(__name__)

Behavior

When a File Is Run Directly

python3 abbas.py

Output:

__main__

• This means the file is the entry point of the program.

When a File Is Imported

import abbas

Output:

abbas

• __name__ is set to the module name, not __main__.

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5. Why __name__ == "__main__" Is Important

This pattern allows code to run only when the file is executed directly, not when imported.

Example

def main():
    print("Running directly")

if __name__ == "__main__":
    main()

Explanation

• The code inside the if block runs only when the file is executed directly.
• Prevents unwanted execution when the file is imported as a module.
• This is a standard Python best practice.

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Summary

• Module: A single .py file
• Package: A directory containing modules
• __init__.py: Marks a directory as a package
• import module: Imports the whole module
• from module import item: Imports specific items
• __name__: Identifies how a file is executed