Creating Packages in Python

Learn how to create your own Python package, organize modules and import them into another Python program.

What is a Python Package?

A package is a directory that organizes related Python modules together.

Packages are useful when a project contains many modules and we want to keep related code together.

Why Do We Create Packages?

• Organize large projects.
• Group related modules.
• Reuse code easily.
• Make applications easier to maintain.
• Separate different parts of an application.

Package Creation Diagram

A package can contain multiple Python modules.

Step 1: Create a Package Folder

First, create a folder for the package.

Example package name: student_package

student_package/

This folder will contain the related Python modules.

Step 2: Create __init__.py

Inside the package folder, we can create a file named __init__.py.

student_package/
|
|-- __init__.py

The file can be empty for a basic package.

It can also contain package initialization code when needed.

Step 3: Create a Module

Now create a module called student.py.

student_package/
|
|-- __init__.py
|
|-- student.py

Add the following code inside student.py:

class Student:

    def __init__(self, name, course):
        self.name = name
        self.course = course

    def display(self):
        print("Name:", self.name)
        print("Course:", self.course)

Step 4: Add Another Module

Let's create another module called marks.py.

student_package/
|
|-- __init__.py
|
|-- student.py
|
|-- marks.py

Add this code to marks.py:

def calculate_total(marks):

    return sum(marks)


def calculate_average(marks):

    return sum(marks) / len(marks)

Final Package Structure

myproject/
|
|-- main.py
|
|-- student_package/
    |
    |-- __init__.py
    |
    |-- student.py
    |
    |-- marks.py

Here:

• myproject is the project folder.
• student_package is the package.
• student.py is one module.
• marks.py is another module.
• main.py is the main program.

Importing a Module from a Package

Now we can import the student module from the package.

In main.py:

from student_package import student

student1 = student.Student(
    "Rahul",
    "Python"
)

student1.display()

Output:

Name: Rahul
Course: Python

Importing a Class Directly

We can also import the class directly from the module.

from student_package.student import Student

student1 = Student(
    "Priya",
    "Python Full Stack"
)

student1.display()

Output:

Name: Priya
Course: Python Full Stack

Importing a Function from a Package

We can import functions from a package module.

from student_package.marks import calculate_total

marks = [80, 75, 90, 85]

total = calculate_total(marks)

print("Total:", total)

Output:

Total: 330

Importing Multiple Items

We can import multiple functions from the same module.

from student_package.marks import (
    calculate_total,
    calculate_average
)

marks = [80, 75, 90, 85]

print("Total:", calculate_total(marks))
print("Average:", calculate_average(marks))

Output:

Total: 330
Average: 82.5

Using __init__.py

The __init__.py file can contain package initialization code.

For example:

print("student_package loaded")

When the package is imported, this initialization code can run according to how the package is imported.

Package with Multiple Modules

A larger package can contain many related modules.

training/
|
|-- __init__.py
|
|-- students.py
|
|-- courses.py
|
|-- trainers.py
|
|-- fees.py
|
|-- reports.py

Each module has its own responsibility.

This makes the project easier to understand and maintain.

Practical Example

Suppose we create a package called calculator_package.

Folder structure:

calculator_project/
|
|-- main.py
|
|-- calculator_package/
    |
    |-- __init__.py
    |
    |-- addition.py
    |
    |-- multiplication.py

addition.py

def add(a, b):

    return a + b

multiplication.py

def multiply(a, b):

    return a * b

main.py

from calculator_package.addition import add
from calculator_package.multiplication import multiply

print(add(10, 20))
print(multiply(5, 4))

Output:

30
20

Module vs Package

Benefits of Creating Packages

• Better project organization.
• Easy code reuse.
• Related modules stay together.
• Easier maintenance.
• Better separation of responsibilities.

Common Mistakes

• Using the wrong package or module name.
• Writing the wrong import path.
• Creating modules outside the expected package directory.
• Confusing a package name with a module name.
• Running the program from an unexpected project location and getting import errors.

Practice Programs

1. Create a package named student_package.
2. Add student.py to the package.
3. Add marks.py to the package.
4. Create a main.py file outside the package.
5. Import a class from student.py.
6. Import a function from marks.py.
7. Create a second package for calculator operations.