77 commands · 5 cheat sheets · Python

Packages, Testing, and Quality master quick reference

Browse 77 commands from 5 focused cheat sheets on page 1 of 1. Each example opens its matching detailed section.

Packages, Testing, and Quality · 15 commands

Python importlib, Metadata, Resources, and Plugins Cheat Sheet

Use	Syntax	Examples
Import by name	`module = importlib.import_module('package.module')`	View examples
Resolve a relative import	`module = importlib.import_module('.codec', package='app.plugins')`	View examples
Find a module specification	`spec = importlib.util.find_spec('package.module')`	View examples
Invalidate finder caches	`importlib.invalidate_caches()`	View examples
Read a distribution version	`release = importlib.metadata.version('distribution-name')`	View examples
Read core metadata	`details = importlib.metadata.metadata('distribution-name')`	View examples
Read declared requirements	`requirements = importlib.metadata.requires('distribution-name') or []`	View examples
Map import to distributions	`owners = importlib.metadata.packages_distributions().get('import_name', [])`	View examples
Get a resource root	`root = importlib.resources.files('package_name')`	View examples
Read a text resource	`text = root.joinpath('data/defaults.ini').read_text(encoding='utf-8')`	View examples
Materialize a resource path	`with importlib.resources.as_file(resource) as path: consume(path)`	View examples
Discover a plugin group	`plugins = importlib.metadata.entry_points(group='acme.plugins')`	View examples
Select one entry point	`matches = plugins.select(name='formatter')`	View examples
Load a plugin object	`plugin = entry_point.load()`	View examples
Handle missing distribution metadata	`except importlib.metadata.PackageNotFoundError: use_fallback()`	View examples

Packages, Testing, and Quality · 17 commands

Python Logging and Observability Cheat Sheet

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Use	Syntax	Examples
Create a module logger	`logger = logging.getLogger(__name__)`	View examples
Set a logger threshold	`logger.setLevel(logging.INFO)`	View examples
Defer message formatting	`logger.info('processed %d records', count)`	View examples
Guard expensive diagnostics	`if logger.isEnabledFor(logging.DEBUG): logger.debug('state=%r', build_state())`	View examples
Configure a small application	`logging.basicConfig(level=logging.INFO, format='%(levelname)s:%(name)s:%(message)s')`	View examples
Apply dictionary configuration	`logging.config.dictConfig({'version': 1, 'handlers': handlers, 'root': root})`	View examples
Preserve existing loggers	`config = {'version': 1, 'disable_existing_loggers': False, 'root': root}`	View examples
Add a stream destination	`handler = logging.StreamHandler(sys.stdout)`	View examples
Set a destination threshold	`handler.setLevel(logging.ERROR)`	View examples
Stop duplicate propagation	`logger.propagate = False`	View examples
Attach event context	`logger.info('checkout accepted', extra={'order_id': order_id})`	View examples
Reuse stable context	`request_log = logging.LoggerAdapter(logger, {'request_id': request_id})`	View examples
Record the active exception	`except OSError: logger.exception('configuration load failed')`	View examples
Include exception information	`logger.error('operation failed', exc_info=True)`	View examples
Attribute a helper's caller	`logger.warning('deprecated call', stacklevel=2)`	View examples
Filter one destination	`handler.addFilter(lambda record: record.name != 'app.health')`	View examples
Emit structured records	`handler.setFormatter(JsonFormatter())`	View examples

Packages, Testing, and Quality · 12 commands

Python Modules and Packages Cheat Sheet

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Use	Syntax	Examples
Import a module	`import statistics`	View examples
Import a name	`from pathlib import Path`	View examples
Alias an import	`import collections.abc as cabc`	View examples
Guard script entry	`if __name__ == '__main__': main()`	View examples
Run by module name	`python -m package.module`	View examples
Regular package marker	`package/__init__.py`	View examples
Relative import	`from .formatting import render`	View examples
Declare star-import names	`__all__ = ['Client', 'connect']`	View examples
Inspect module identity	`print(module.__name__)`	View examples
Inspect source location	`print(module.__file__)`	View examples
Find without importing	`spec = importlib.util.find_spec('package.module')`	View examples
Read package data	`text = resources.files('package').joinpath('defaults.json').read_text()`	View examples

Packages, Testing, and Quality · 19 commands

Python Packaging, Virtual Environments, and pyproject.toml Cheat Sheet

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Use	Syntax	Examples
Create a virtual environment	`python -m venv .venv`	View examples
Seed current packaging tools	`python -m venv --upgrade-deps .venv`	View examples
Invoke the environment directly	`.venv/bin/python -m pip --version`	View examples
Declare backend requirements	`requires = ['hatchling>=1.26'] # in [build-system]`	View examples
Select a build backend	`build-backend = 'hatchling.build'`	View examples
Declare Python compatibility	`requires-python = '>=3.11'`	View examples
Declare a runtime dependency	`dependencies = ['httpx>=0.27,<1']`	View examples
Publish a console command	`acme = 'acme.cli:main' # in [project.scripts]`	View examples
Declare an optional feature	`test = ['pytest>=8'] # in [project.optional-dependencies]`	View examples
Apply deployment constraints	`python -m pip install -c constraints.txt -r requirements.txt`	View examples
Require artifact hashes	`python -m pip install --require-hashes -r requirements.txt`	View examples
Use a src package layout	`src/acme/__init__.py`	View examples
Open packaged text	`text = resources.files('acme').joinpath('data.txt').read_text(encoding='utf-8')`	View examples
Build sdist and wheel	`python -m build`	View examples
Build only a wheel	`python -m build --wheel`	View examples
Install the built wheel	`python -m pip install --force-reinstall dist/acme_tools-1.2.0-py3-none-any.whl`	View examples
Validate distribution metadata	`python -m twine check dist/*`	View examples
Upload to TestPyPI	`python -m twine upload --repository testpypi dist/*`	View examples
Read installed metadata	`version = importlib.metadata.version('acme-tools')`	View examples

Packages, Testing, and Quality · 14 commands

Python unittest and Mocking Cheat Sheet

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Use	Syntax	Examples
Create a test case	`class ParserTests(unittest.TestCase): ...`	View examples
Declare a test	`def test_rejects_empty_input(self): ...`	View examples
Compare values	`self.assertEqual(actual, expected)`	View examples
Assert an exception	`with self.assertRaises(ValueError): parse('')`	View examples
Assert message text	`with self.assertRaisesRegex(ValueError, 'positive'): validate(0)`	View examples
Prepare each test	`def setUp(self): self.client = Client()`	View examples
Register cleanup	`self.addCleanup(resource.close)`	View examples
Name table cases	`with self.subTest(value=value): self.assertTrue(valid(value))`	View examples
Create a specified mock	`client = Mock(spec=ApiClient)`	View examples
Patch with signature checks	`@patch('module.ApiClient', autospec=True)`	View examples
Configure a return	`client.fetch.return_value = {'status': 'ok'}`	View examples
Raise or vary calls	`client.fetch.side_effect = TimeoutError('slow')`	View examples
Verify one call	`client.fetch.assert_called_once_with('/status')`	View examples
Use a temporary directory	`with tempfile.TemporaryDirectory() as directory: ...`	View examples

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