Why Python Wheels Speed Up Installations and How They Work

Preface

Python .whl files (wheels) are a rarely discussed but crucial part of the package installation process; they make installations faster and more efficient when using pip.

Introduction to Wheels

Wheels are a component of the Python ecosystem that enable faster, more reliable package distribution and installation. This tutorial explores what wheels are, their benefits, and how they simplify using Python.

Installing a Package with Wheels

To experiment, install uWSGI version 2.0.x as usual:

$ python -m pip install 'uwsgi==2.0.*'
Collecting uwsgi==2.0.*
Downloading uwsgi-2.0.18.tar.gz (801 kB)
|████████████████████████████████| 801 kB 1.1 MB/s
Building wheels for collected packages: uwsgi
Building wheel for uwsgi (setup.py) ... done
Created wheel for uwsgi: uWSGI-2.0.18-cp38-cp38-macosx_10_15_x86_64.whl
Stored in directory: /private/var/folders/jc/8_hqsz0x1tdbp05 ...
Successfully built uwsgi
Installing collected packages: uwsgi
Successfully installed uwsgi-2.0.18

pip follows several steps to fully install uWSGI:

Downloads the uwsgi-2.0.18.tar.gz source tarball (gzip‑compressed).

Builds a .whl file from the tarball by invoking setup.py.

Names the wheel uWSGI-2.0.18-cp38-cp38-macosx_10_15_x86_64.whl.

Installs the package from the built wheel.

The tar.gz retrieved by pip is a source distribution (sdist), which is essentially the opposite of a wheel. An sdist contains the package’s source code, including any C/C++ extension modules, and a .egg-info metadata directory.

From a developer’s perspective, creating an sdist is done with:

$ python setup.py sdist

Installing a Package that Provides a Wheel

Now install chardet:

$ python -m pip install 'chardet==3.*'
Collecting chardet
Downloading chardet-3.0.4-py2.py3-none-any.whl (133 kB)
|████████████████████████████████| 133 kB 1.5 MB/s
Installing collected packages: chardet
Successfully installed chardet-3.0.4

Here pip directly downloads a pre‑built wheel ( chardet-3.0.4-py2.py3-none-any.whl), so no build step occurs.

From a developer’s side, a wheel is produced by running: $ python setup.py bdist_wheel Why does uWSGI provide only an sdist while chardet offers a wheel? Checking the project’s page on PyPI reveals that uWSGI only distributes a source tarball, whereas chardet supplies both a wheel and an sdist; pip prefers the wheel when it matches the environment.

Other packages, such as psycopg2, illustrate platform‑specific wheel availability (many wheels for Windows, none for Linux/macOS).

Wheels Accelerate Installation

Wheels speed up installation for two main reasons:

Wheels are usually smaller than source distributions, reducing network transfer time.

Installing from a wheel skips the intermediate build step required for sdists.

For example, installing chardet takes only a fraction of the time needed for uWSGI. To compare more directly, you can force pip to ignore wheels with the --no-binary=:all: option:

$ time python -m pip install \
    --no-cache-dir \
    --force-reinstall \
    --no-binary=:all: \
    cryptography

This forces a source‑only installation of cryptography, which on the author’s machine took about 32 seconds, including the need for OpenSSL development headers.

Re‑installing with wheels (or using --only-binary=:all:) reduces the time to just over 4 seconds, roughly one‑eighth of the source‑only duration.

Original source: https://developer.51cto.com/art/202008/623418.htm – Author: Machine Learning and Data Analysis