Python Wheels Intro

Table of Contents:

• Elementary info about the Python wheel
• Example of a wheel file format
• Ways to install Python package
• Summary

Elementary info about the Python wheel

A Python wheel with the extension .whl is a zip file.

Try to rename file.whl to file.whl.zip and you will be able to unzip it.

Wheels contain both Python package files (.py) and metadata.

Wheels are installed using pip.

You should not find any .pyc files inside a wheel. pip automatically generates .pyc files.

In order to work with Python .whl files you need wheel and setuptools>=0.8 installed.

Example: Update your wheels

$pip install -U wheel setuptools

Example of a wheel file format

Let’s take for instance pandas wheel:

pandas-1.3.3-cp37-cp37m-macosx_10_9_x86_64.whl

We can read as follows:

pandas             = package name
1.3.3              = package version
macosx_10_9_x86_64 = platform
cp37               = CPython 3.7 implementation
cp37m              = as before but with pymalloc extension

Some other Python implementations we may find instead of CPython (cp):

• IronPython (Python for .NET)
• Jython (Python for Java)
• PyPy (Python JIT)
• MicroPython (Python for microcontrollers)

Now we understand we create Python wheels for different platforms and different Python implementations.

If you would create a wheel for any platform the file name would be:

pandas-1.3.3-cp37-cp37m-any.whl

If your project is pure Python then you will use “any” keyword and create a pure Python wheel.

If your project contains compiled extensions, then you will create platform specific wheel.

Ways to install Python package

In Python you can install packages several ways:

• from source files directly
• from git branches, tags, or hashes (similar as source files).
• from egg file (replaced by wheel)
• from zip file (.zip file)
• from wheel (.whl file)

Here we will provide examples for the last two options:

Example installing the package from zip file:

pip install https://github.com/user/repository/archive/branch.zip

Example installing the package from .whl file:

pip install https://github.com/user/repository/archive/branch.whl

Wheels is the fastest way to install Python packages thus it is preferred way.

Wheels are often smaller than source distributions, but this may not always be the case.

Where is the Python wheel metadata

If you unzip a .whl file you can find metadata info in a file called METADATA inside .dist-info folder.

Example of a keras wheel METADATA file:

Metadata-Version: 2.1
Name: keras
Version: 2.6.0
Summary: TensorFlow Keras.
Home-page: https://keras.io/
Author: Google Inc.
Author-email: [email protected]
License: Apache 2.0
Download-URL: https://github.com/keras-team/keras/tags
Keywords: tensorflow keras tensor machine learning
Platform: UNKNOWN
...

Summary

Wheel was introduced in 2012 as a packaging format to install a package without building or compilation, thus it is fast.

Wheel came through PEP (Python Enhancement Proposal). Wheels do not have .pyc files inside. You can check the contents of a wheel if you unzip it.