setuptools

Learn packaging with setuptools.

setuptools

setuptools is a tool that builds Python packages and uploads them to PyPI. In modern usage it is not called directly; it is declared in the [build-system] table inside pyproject.toml.

[build-system]
requires = ["setuptools>=61"]
build-backend = "setuptools.build_meta"

requires lists the packages needed to build; build-backend names the backend to run. This tells pip install which tool to use.

The [build-system] table

The [build-system] table has two main fields. requires is the list of packages installed during build; build-backend is the dotted path to the Python object that drives the build.

[build-system]
requires = ["setuptools>=61"]
build-backend = "setuptools.build_meta"

The setuptools build_meta backend builds a wheel from source. Without this configuration pip install would not know which tool to call.

Exercise Read the build-backend with tomllib

Start with import tomllib. Convert the TOML string below into structured data with tomllib.loads(...) and assign it to data:

[build-system]
requires = ["setuptools>=61"]
build-backend = "setuptools.build_meta"

Then print the backend path with print(data["build-system"]["build-backend"]).

Show example solution

import tomllib

data = tomllib.loads('''
[build-system]
requires = ["setuptools>=61"]
build-backend = "setuptools.build_meta"
''')

print(data["build-system"]["build-backend"])

Test yourself

Complete the build-backend line

[build-system]
requires = ["setuptools>=61"]
____ = "setuptools.build_meta"

Show answer

[build-system]
requires = ["setuptools>=61"]
build-backend = "setuptools.build_meta"

What does setuptools.build_meta do?
- Uploads the package to PyPI
- Builds a wheel from source
- Creates a virtual environment
- Freezes dependencies
Show answer

Builds a wheel from source — build_meta builds a wheel from source.
Match the setuptools concepts

setuptools

Build tool
build_meta

Produces a wheel
requires

Build packages
wheel

Installable artifact

Next lesson: Virtual environment

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