5 steps to build your first Python package

Following 5 steps, you can build your own Python packages/libraries.

You may have used a lot of Python packages/libraries in your daily work, such as Pandas. Have you wondered how those libraries are built? By following a few steps, you can build your own package/library as well just like any major Python libraries. You can also share it on Github and let the open-source spirit shine. Because this is the way! Let’s get started!

1. Use Github to create a project repository

First, we need to create a repo on Github. Like the screenshot below, click the green “New” button to create a new repo on your Github.

Then we can give the package a name. Let’s say “mydates”. We can also add some description in the “Description” session. After that, we can set the repo to be “Public” and select “Add a README file”, which will make Github create a README markdown file when creating the new repo. Remember to choose .gitignore and license file. The .gitignore file can help us avoid subm itting some intermediate development files to the git repository.

2. Download git repository

Find the git address of your repository, and download the code to your local directory by running the following command in your terminal. Of course, you need to replace “MeasureSpace” with your own Github name.

git clone https://github.com/MeasureSpace/mydates.git

3. Package structure

Now it’s time to desgin our package structure. We are going to write a simple package called mydates with two modules - Dates and core.

• Dates module has one class Important_Dates. This class is initialized with two variables: birth_day and wedding_day, and then uses two functions get_days_passed_in_my_life() and get_days_passed_in_marriage() to calculate the number of days passed.
• The core module has one test function print_test() which just prints a test sentence.

We put the two modules under folder mydates. Here mydates is the name of our package. Under mydates folder we create an initial file __initi__.py to tell Python automatically include all the module files. The content of the __init__.py file is as follow:

from .core import *
from . import Dates

We show two different ways of including modules above. The statement from .core import * indicates that you can directly import functions from the package mydates such as from mydates import print_test. The statement from . import Dates means that we need to import Dates modules first such as from mydates import Dates in order to use classes or functions in Dates module.

Afte we have modules ready, we create another folder scripts for our script get_my_date.py. It’s a test script as follow:

from mydates import Dates
from mydates import print_test

birth_day = '1999-09-09'
wedding_day = '2012-05-09'

mydays = Dates.Important_Dates(birth_day, wedding_day)

mydays.get_days_passed_in_my_life()

mydays.get_days_passed_in_marriage()

print_test()

The whole structure of the package is as follow.

4. Write setup.py file

To install the package mydates, we need to write a setup.py file as follow:

from distutils.core import setup

setup(
    name='mydates',
    version='0.0.1',
    author='Measure Space',
    author_email='xx@example.com',
    url='www.example.com',
    license='LICENSE',
    packages=['mydates'],
    description='An example of building a Python package.',
    install_requires=[
    'python>=3.0.0',
    'pandas>=0.1.0'
    ]
)

Most time we need to install some required packages that are used in our own package. There are two ways to do so.

• Write them under install_requires dictionary in setup.py
• Write your own requirements.txt

The second method is a preferred method as it gives the most comprehensive list of all required packages. The detailed difference of these two methods can be found at here. One example of the requirements.txt is as follow:

python>=3.0.0
pandas>=0.1.0

5. Two ways of installing your package

Now we can install our first Python package mydates. There are also two ways we can use to install the package.

• Official mode: run pip install . in your terminal under the package root folder. This is similar as installing other Python packages.
• Development mode: Also under the package root folder, run pip install -e . In this way, any changes we made can be reflected to the package immediately. This is the typical way of installing a development package.

Once we install the package, we can go to scripts folder and run the test script get_my_dates.py, it gives us the following results.

You have been living in this world for 7192 days!
You have been married for 2566 days!
This is a test.

Congrats! You’ve developed your first Python package!