Package structure and usage in Python - Step-by-Step Execution

Concept Flow - Package structure and usage

Create package folder

↓

Add __init__.py file

↓

Add modules (python files)

↓

Import package/module in main script

↓

Use functions/classes from package

↓

Run main script

This flow shows how to create a package folder with __init__.py, add modules, import them, and use their contents in a main script.

Execution Sample

Python

mypackage/
  __init__.py
  greetings.py

# greetings.py
def say_hello():
    return 'Hello!'

# main.py
from mypackage.greetings import say_hello
output = say_hello()
print(output)

This code creates a package with a greetings module and uses its function in main.py to print a greeting.

Execution Table

Step	Action	File/Module	Result/Output
1	Create folder 'mypackage' and add __init__.py	mypackage/__init__.py	Package recognized by Python
2	Write function say_hello in greetings.py	mypackage/greetings.py	Function say_hello defined
3	Import say_hello from mypackage.greetings in main.py	main.py	say_hello function available
4	output = say_hello()	main.py	output = 'Hello!'
5	print(output)	main.py	Output: Hello!

💡 Program ends after printing the greeting.

Variable Tracker

Variable	Start	After call	Final
say_hello	function defined	called	returned 'Hello!'
output	undefined	'Hello!'	'Hello!'

Key Moments - 3 Insights

Why do we need the __init__.py file in the package folder?

The __init__.py file tells Python this folder is a package, so imports like 'from mypackage.greetings' work. See execution_table step 1.

How does Python find the say_hello function when we import it?

Python looks inside the greetings.py module in the mypackage folder because of the import statement in step 3.

What happens if we forget to call the function before printing?

If we print say_hello without parentheses, it prints the function object, not the string. See step 4 and 5 for correct call.

Visual Quiz - 3 Questions

Look at the execution_table, at which step is the package recognized by Python?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Check the 'Result/Output' column for when the package is recognized.

According to variable_tracker, what is the value of 'output' after the function call?

A function object

B 'Hello!'

C undefined

D None

💡 Hint

Look at the 'After call' and 'Final' columns for 'output' variable.

If we remove __init__.py from the package folder, what will happen when importing?

A Import will fail because Python won't recognize the folder as a package

B Import will work normally

C Function will return None

D Python will run the function automatically

💡 Hint

Refer to key_moments about the role of __init__.py and execution_table step 1.

Concept Snapshot

Package structure in Python:
- Create a folder for the package
- Add __init__.py file inside (can be empty)
- Add modules (python files) inside the folder
- Import modules/functions using 'from package.module import func'
- Use imported functions/classes in your script
- Run the script to use the package

Full Transcript

To create a Python package, first make a folder and add an __init__.py file inside it. This file tells Python the folder is a package. Then add Python files (modules) with functions or classes. In your main script, import what you need from the package modules. Call the functions and print or use their results. The execution table shows each step: creating the package, defining functions, importing, calling, and printing output. Variables track the function and output values. Key moments explain why __init__.py is needed and how imports work. The quiz tests understanding of these steps and concepts.