Flit

Warnings

• breaking Flit 3.0 removed support for the older `flit.ini` configuration file format. Projects must now use `pyproject.toml` for all metadata.
  Fix: Convert `flit.ini` to `pyproject.toml` by running `python3 -m flit.tomlify` in your project directory. Ensure `[build-system]` and `[project]` tables are correctly configured according to PEP 621.
• breaking The `flit_core` build backend, which Flit uses, now explicitly requires Python 3. This means that while Flit can package Python 2 modules, it must be run on a Python 3 interpreter.
  Fix: Always install and run Flit using a Python 3 environment (e.g., `python3 -m pip install flit`). Ensure your project's `pyproject.toml` specifies `requires-python` appropriately.
• deprecated In Flit 3.5, the default behavior of `flit build` and `flit publish` changed; they no longer generate a `setup.py` file in the sdist by default. This makes sdists only compatible with tools supporting PEP 517.
  Fix: If you need to support older installers that do not support PEP 517 and require a `setup.py`, you can explicitly include it during `flit build` or `flit publish` (check documentation for specific flags if needed, though typically `--sdist-include-setup-py` was removed in favor of `pyproject.toml` configuration).
• gotcha Flit is designed for pure Python packages without complex build steps (e.g., C extensions, bundled Javascript). If your project requires compilation or other build processes, Flit may not be the most suitable tool.
  Fix: For projects with complex build requirements, consider alternative tools like Setuptools or Hatchling, which are designed to handle such scenarios.
• gotcha Flit does not manage your project's dependencies directly; you must declare them in `pyproject.toml` manually. Tools like Poetry or Pipenv offer integrated dependency management.
  Fix: Ensure all external package dependencies are accurately listed in the `[project.dependencies]` section of your `pyproject.toml`.

Install

• pip install flit Install Flit

Imports

• flit

  Flit is primarily a command-line tool. Direct Python imports for typical packaging tasks are not common.

  Users interact with Flit via its command-line interface (e.g., `flit init`, `flit build`, `flit publish`). The `flit_core` package provides the PEP 517 build backend, with its public API at `flit_core.buildapi`, which is generally used by build frontends, not directly by end-user Python code.

Quickstart

To get started with Flit, first create your Python module or package with a `__version__` attribute. Then, navigate to your project's root directory and run `flit init` to generate a `pyproject.toml` file. This file will contain your package's metadata. You can then build your distribution files using `flit build` and publish them to PyPI with `flit publish`.

# Create a directory for your package, e.g., 'my_package'
# Inside 'my_package', create 'my_module.py' or a package directory 'my_module/__init__.py'

# my_module/__init__.py (or my_module.py)
"""An amazing sample package!"""
__version__ = "0.1.0"

def greet(name):
    return f"Hello, {name}!"

# In the root of your package directory (e.g., 'my_package')
# 1. Initialize Flit (creates pyproject.toml)
# flit init

# This would be the content of the generated pyproject.toml (adjust details):
# [build-system]
# requires = ["flit_core >=3.2,<4"]
# build-backend = "flit_core.buildapi"

# [project]
# name = "my-module-name"
# authors = [{name = "Your Name", email = "your.email@example.com"}]
# dynamic = ["version", "description"]
# classifiers = [
#     "Programming Language :: Python :: 3",
#     "License :: OSI Approved :: MIT License",
#     "Operating System :: OS Independent",
# ]
# requires-python = ">=3.8"

# 2. Build the package (creates .whl and .tar.gz in 'dist/')
# flit build

# 3. Publish to PyPI (requires PyPI credentials setup)
# flit publish --repository pypi

# Example of using the installed package locally:
# pip install --no-index --find-links=./dist my-module-name

# import my_module
# print(my_module.greet("Flit User"))