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FAQ

Interoperability

Q: What is the risk of lock-in?

A: Not much! Other than the plugin system, everything uses Python's established standards by default. Project metadata is based entirely on the standard, the build system is compatible with PEP 517/PEP 660, versioning uses the scheme specified by PEP 440, dependencies are defined with PEP 508 strings, and environments use virtualenv.

Q: Must one use all features?

A: No, all features are optional! You can use just the build system, publish wheels and source distributions that were built by other tools, only use the environment management, etc.

Libraries vs applications

Q: Are workflows for both libraries and applications supported?

A: Yes, mostly! Applications can utilize environment management just like libraries, and plugins can be used to build projects in arbitrary formats or publish artifacts to arbitrary destinations.

The only caveat is that currently there is no support for re-creating an environment given a set of dependencies in a reproducible manner. Although a standard lock file format may be far off since [PEP 665][] was rejected, resolving capabilities are coming to pip. When that is stabilized, Hatch will add locking functionality and dedicated documentation for managing applications.

Tool migration

Q: How to migrate to Hatch?

Build system

import os
from io import open

from setuptools import find_packages, setup

about = {}
with open(os.path.join('src', 'foo', '__about__.py'), 'r', 'utf-8') as f:
    exec(f.read(), about)

with open('README.md', 'r', 'utf-8') as f:
    readme = f.read()

setup(
    # Metadata
    name='foo',
    version=about['__version__'],
    description='...',
    long_description=readme,
    long_description_content_type='text/markdown',
    author='...',
    author_email='...',
    project_urls={
        'Documentation': '...',
        'Source': '...',
    },
    classifiers=[
        '...',
    ],
    keywords=[
        '...',
    ],
    python_requires='>=3.8',
    install_requires=[
        '...',
    ],
    extras_require={
        'feature': ['...'],
    },

    # Packaging
    packages=find_packages(where='src'),
    package_dir={'': 'src'},
    package_data={
        'foo': ['py.typed'],
    },
    zip_safe=False,
    entry_points={
        'console_scripts': [
            'foo = foo.cli:main',
        ],
    },
)

graft tests

global-exclude *.py[cod] __pycache__

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

[project]
name = "foo"
description = "..."
readme = "README.md"
authors = [
  { name = "...", email = "..." },
]
classifiers = [
  "...",
]
keywords = [
  "...",
]
requires-python = ">=3.8"
dependencies = [
  "...",
]
dynamic = ["version"]

[project.urls]
Documentation = "..."
Source = "..."

[project.optional-dependencies]
feature = ["..."]

[project.scripts]
foo = "foo.cli:main"

[tool.hatch.version]
path = "src/foo/__about__.py"

[tool.hatch.build.targets.sdist]
include = [
  "/src",
  "/tests",
]

Environments

Invocation:

tox

[tox]
envlist =
    py{27,38}-{42,3.14}
    py{38,39}-{9000}-{foo,bar}

[testenv]
usedevelop = true
deps =
    coverage[toml]
    pytest
    pytest-cov
    foo: cryptography
commands =
    pytest --cov-report=term-missing --cov-config=pyproject.toml --cov=pkg --cov=tests {posargs}
setenv =
    3.14: PRODUCT_VERSION=3.14
    42: PRODUCT_VERSION=42
    9000: PRODUCT_VERSION=9000
    {foo,bar}: EXPERIMENTAL=true

Invocation:

hatch run test

[tool.hatch.envs.default]
dependencies = [
  "coverage[toml]",
  "pytest",
  "pytest-cov",
]

[tool.hatch.envs.default.scripts]
test = 'pytest --cov-report=term-missing --cov-config=pyproject.toml --cov=pkg --cov=tests'

[tool.hatch.envs.default.overrides]
matrix.version.env-vars = "PRODUCT_VERSION"
matrix.features.env-vars = "EXPERIMENTAL=true"
matrix.features.dependencies = [
  { value = "cryptography", if = ["foo"] },
]

[[tool.hatch.envs.default.matrix]]
python = ["2.7", "3.8"]
version = ["42", "3.14"]

[[tool.hatch.envs.default.matrix]]
python = ["3.8", "3.9"]
version = ["9000"]
features = ["foo", "bar"]

[envs.default]
dependencies = [
  "coverage[toml]",
  "pytest",
  "pytest-cov",
]

[envs.default.scripts]
test = 'pytest --cov-report=term-missing --cov-config=pyproject.toml --cov=pkg --cov=tests'

[envs.default.overrides]
matrix.version.env-vars = "PRODUCT_VERSION"
matrix.features.env-vars = "EXPERIMENTAL=true"
matrix.features.dependencies = [
  { value = "cryptography", if = ["foo"] },
]

[[envs.default.matrix]]
python = ["2.7", "3.8"]
version = ["42", "3.14"]

[[envs.default.matrix]]
python = ["3.8", "3.9"]
version = ["9000"]
features = ["foo", "bar"]

Fast CLI?

The claim about being faster than other tools is based on timings that are always checked in CI.

Hatch achieves this by using lazy imports, lazily performing computation manually and with functools.cached_property, using hacks like not not ... instead of bool(...), etc.