Enabling Python support
How to enable Pants's bundled Python backend package.
Example Python repository
See here for examples of Pants's Python functionality.
See here for Django-specific examples.
Enable the Python backend like this:
[GLOBAL] ... backend_packages = [ "pants.backend.python" ]
python_test targets to know which Python files to run on and to set any metadata.
To reduce boilerplate, the
python_sources target generates a
python_source target for each file in its
sources field, and
python_tests generates a
python_test target for each file in its
python_sources(name="lib", sources=["dirutil.py", "strutil.py"]) python_tests(name="tests", sources=["strutil_test.py"]) # Spiritually equivalent to: python_source(name="dirutil", source="dirutil.py") python_source(name="strutil", source="strutil.sh") python_test(name="strutil_test.py", source="strutil_test.py") # Thanks to the default `sources` values, spiritually equivalent to: python_sources(name="lib") python_tests(name="tests")
You can generate these targets by running
Created project/BUILD: - Add python_sources target project - Add python_tests target tests
Have content in your
Pants automatically uses all relevant
__init__.pyfiles, even if dependency inference does not include the files and you don't add it to the
dependenciesfields of your targets.
This works if you have empty
__init__.pyfiles, like most Python projects do; but if you have actual code in your
__init__.pyfiles, you should turn on both of these options in your
[python] tailor_ignore_solitary_init_files = false [python-infer] inits = true
This option will cause Pants to infer "proper" dependencies on any ancestor
__init__.pyfile. If you run
./pants dependencies project/util/foo.py, you should see
project/util/__init__.pyshow up. This will ensure that any of the
__init__.pyfiles are included.
macOS users: you may need to change interpreter search paths
By default, Pants will look at both your
$PATHand—if you use Pyenv—your
$(pyenv root)/versionsfolder when discovering Python interpreters. Your
$PATHlikely includes the system Pythons at
/usr/bin/python3, which are known to have many issues like failing to install some dependencies.
Pants will prefer new Python versions, like 3.6.10 over 3.6.3. Because macOS system Pythons are usually very old, they will usually be ignored.
However, if you run into issues, you can set the
interpreter_search_pathsoption in the
[python] interpreter_search_paths = [ # This will use all interpreters in `$(pyenv root)/versions`. "<PYENV>", # Brew usually installs Python here. "/usr/local/bin", ]
See here for more information.
Updated over 1 year ago