Python Rules

Rules

• py_binary
• py_library
• py_test
• py_runtime

py_binary

View rule sourceopen_in_new

py_binary(name, deps, srcs, data, args, compatible_with, deprecation, distribs, env, exec_compatible_with, exec_properties, features, imports, legacy_create_init, licenses, main, output_licenses, precompile, precompile_invalidation_mode, precompile_optimize_level, precompile_source_retention, pyc_collection, python_version, restricted_to, srcs_version, stamp, tags, target_compatible_with, testonly, toolchains, visibility)

Arguments

Attributes
name	Name; required A unique name for this target.
deps	List of labels; default is [] List of additional libraries to be linked in to the target. See comments about the deps attribute typically defined by rules. These are typically py\_library rules. Targets that only provide data files used at runtime belong in the data attribute.
srcs	List of labels; required The list of Python source files that are processed to create the target. This includes all your checked-in code and may include generated source files. The .py files belong in srcs and library targets belong in deps. Other binary files that may be needed at run time belong in data.
data	List of labels; default is [] The list of files need by this library at runtime. See comments about the data attribute typically defined by rules. There is no py\_embed\_data like there is cc\_embed\_data and go\_embed\_data. This is because Python has a concept of runtime resources.
imports	List of strings; default is [] List of import directories to be added to the PYTHONPATH. Subject to “Make variable” substitution. These import directories will be added for this rule and all rules that depend on it (note: not the rules this rule depends on. Each directory will be added to PYTHONPATH by py\_binary rules that depend on this rule. The strings are repo-runfiles-root relative, Absolute paths (paths that start with /) and paths that references a path above the execution root are not allowed and will result in an error.
legacy_create_init	Integer; default is -1 Whether to implicitly create empty \_\_init\_\_.py files in the runfiles tree. These are created in every directory containing Python source code or shared libraries, and every parent directory of those directories, excluding the repo root directory. The default, -1 (auto), means true unless --incompatible\_default\_to\_explicit\_init\_py is used. If false, the user is responsible for creating (possibly empty) \_\_init\_\_.py files and adding them to the srcs of Python targets as required.
main	Label; default is None Optional; the name of the source file that is the main entry point of the application. This file must also be listed in srcs. If left unspecified, name, with .py appended, is used instead. If name does not match any filename in srcs, main must be specified.
precompile	String; default is "inherit" Whether py source files **for this target** should be precompiled. Values: * inherit: Allow the downstream binary decide if precompiled files are used. * enabled: Compile Python source files at build time. * disabled: Don’t compile Python source files at build time. ::: * The --precompile flag, which can override this attribute in some cases and will affect all targets when building. * The pyc\_collection attribute for transitively enabling precompiling on a per-target basis. * The Precompiling docs for a guide about using precompiling. :::
precompile_invalidation_mode	String; default is "auto" How precompiled files should be verified to be up-to-date with their associated source files. Possible values are: * auto: The effective value will be automatically determined by other build settings. * checked\_hash: Use the pyc file if the hash of the source file matches the hash recorded in the pyc file. This is most useful when working with code that you may modify. * unchecked\_hash: Always use the pyc file; don’t check the pyc’s hash against the source file. This is most useful when the code won’t be modified. For more information on pyc invalidation modes, see https://docs.python.org/3/library/py\_compile.html#py\_compile.PycInvalidationMode
precompile_optimize_level	Integer; default is 0 The optimization level for precompiled files. For more information about optimization levels, see the compile() function’s optimize arg docs at https://docs.python.org/3/library/functions.html#compile NOTE: The value -1 means “current interpreter”, which will be the interpreter used _at build time when pycs are generated_, not the interpreter used at runtime when the code actually runs.
precompile_source_retention	String; default is "inherit" Determines, when a source file is compiled, if the source file is kept in the resulting output or not. Valid values are: * inherit: Inherit the value from the --precompile\_source\_retention flag. * keep\_source: Include the original Python source. * omit\_source: Don’t include the original py source.
pyc_collection	String; default is "inherit" Determines whether pyc files from dependencies should be manually included. Valid values are: * inherit: Inherit the value from --precompile. * include\_pyc: Add implicitly generated pyc files from dependencies. i.e. pyc files for targets that specify precompile="inherit". * disabled: Don’t add implicitly generated pyc files. Note that pyc files may still come from dependencies that enable precompiling at the target level.
python_version	String; default is "PY3" Defunct, unused, does nothing.
srcs_version	String; default is "PY2AND3" Defunct, unused, does nothing.
stamp	Integer; default is -1 Whether to encode build information into the binary. Possible values: * stamp = 1: Always stamp the build information into the binary, even in --nostamp builds. **This setting should be avoided**, since it potentially kills remote caching for the binary and any downstream actions that depend on it. * stamp = 0: Always replace build information by constant values. This gives good build result caching. * stamp = -1: Embedding of build information is controlled by the --[no]stamp flag. Stamped binaries are not rebuilt unless their dependencies change. WARNING: Stamping can harm build performance by reducing cache hits and should be avoided if possible.

py_library

View rule sourceopen_in_new

py_library(name, deps, srcs, data, compatible_with, deprecation, distribs, exec_compatible_with, exec_properties, features, imports, licenses, precompile, precompile_invalidation_mode, precompile_optimize_level, precompile_source_retention, restricted_to, srcs_version, tags, target_compatible_with, testonly, toolchains, visibility)

A library of Python code that can be depended upon. Default outputs: * The input Python sources * The precompiled artifacts from the sources. NOTE: Precompilation affects which of the default outputs are included in the resulting runfiles. See the precompile-related attributes and flags for more information. ::: 0.37.0 Source files are no longer added to the runfiles directly. :::

Arguments

Attributes
name	Name; required A unique name for this target.
deps	List of labels; default is [] List of additional libraries to be linked in to the target. See comments about the deps attribute typically defined by rules. These are typically py\_library rules. Targets that only provide data files used at runtime belong in the data attribute.
srcs	List of labels; default is [] The list of Python source files that are processed to create the target. This includes all your checked-in code and may include generated source files. The .py files belong in srcs and library targets belong in deps. Other binary files that may be needed at run time belong in data.
data	List of labels; default is [] The list of files need by this library at runtime. See comments about the data attribute typically defined by rules. There is no py\_embed\_data like there is cc\_embed\_data and go\_embed\_data. This is because Python has a concept of runtime resources.
imports	List of strings; default is [] List of import directories to be added to the PYTHONPATH. Subject to “Make variable” substitution. These import directories will be added for this rule and all rules that depend on it (note: not the rules this rule depends on. Each directory will be added to PYTHONPATH by py\_binary rules that depend on this rule. The strings are repo-runfiles-root relative, Absolute paths (paths that start with /) and paths that references a path above the execution root are not allowed and will result in an error.
precompile	String; default is "inherit" Whether py source files **for this target** should be precompiled. Values: * inherit: Allow the downstream binary decide if precompiled files are used. * enabled: Compile Python source files at build time. * disabled: Don’t compile Python source files at build time. ::: * The --precompile flag, which can override this attribute in some cases and will affect all targets when building. * The pyc\_collection attribute for transitively enabling precompiling on a per-target basis. * The Precompiling docs for a guide about using precompiling. :::
precompile_invalidation_mode	String; default is "auto" How precompiled files should be verified to be up-to-date with their associated source files. Possible values are: * auto: The effective value will be automatically determined by other build settings. * checked\_hash: Use the pyc file if the hash of the source file matches the hash recorded in the pyc file. This is most useful when working with code that you may modify. * unchecked\_hash: Always use the pyc file; don’t check the pyc’s hash against the source file. This is most useful when the code won’t be modified. For more information on pyc invalidation modes, see https://docs.python.org/3/library/py\_compile.html#py\_compile.PycInvalidationMode
precompile_optimize_level	Integer; default is 0 The optimization level for precompiled files. For more information about optimization levels, see the compile() function’s optimize arg docs at https://docs.python.org/3/library/functions.html#compile NOTE: The value -1 means “current interpreter”, which will be the interpreter used _at build time when pycs are generated_, not the interpreter used at runtime when the code actually runs.
precompile_source_retention	String; default is "inherit" Determines, when a source file is compiled, if the source file is kept in the resulting output or not. Valid values are: * inherit: Inherit the value from the --precompile\_source\_retention flag. * keep\_source: Include the original Python source. * omit\_source: Don’t include the original py source.
srcs_version	String; default is "PY2AND3" Defunct, unused, does nothing.

py_test

View rule sourceopen_in_new

py_test(name, deps, srcs, data, args, compatible_with, deprecation, distribs, env, env_inherit, exec_compatible_with, exec_properties, features, flaky, imports, legacy_create_init, licenses, local, main, precompile, precompile_invalidation_mode, precompile_optimize_level, precompile_source_retention, pyc_collection, python_version, restricted_to, shard_count, size, srcs_version, stamp, tags, target_compatible_with, testonly, timeout, toolchains, visibility)

Arguments

Attributes
name	Name; required A unique name for this target.
deps	List of labels; default is [] List of additional libraries to be linked in to the target. See comments about the deps attribute typically defined by rules. These are typically py\_library rules. Targets that only provide data files used at runtime belong in the data attribute.
srcs	List of labels; required The list of Python source files that are processed to create the target. This includes all your checked-in code and may include generated source files. The .py files belong in srcs and library targets belong in deps. Other binary files that may be needed at run time belong in data.
data	List of labels; default is [] The list of files need by this library at runtime. See comments about the data attribute typically defined by rules. There is no py\_embed\_data like there is cc\_embed\_data and go\_embed\_data. This is because Python has a concept of runtime resources.
imports	List of strings; default is [] List of import directories to be added to the PYTHONPATH. Subject to “Make variable” substitution. These import directories will be added for this rule and all rules that depend on it (note: not the rules this rule depends on. Each directory will be added to PYTHONPATH by py\_binary rules that depend on this rule. The strings are repo-runfiles-root relative, Absolute paths (paths that start with /) and paths that references a path above the execution root are not allowed and will result in an error.
legacy_create_init	Integer; default is -1 Whether to implicitly create empty \_\_init\_\_.py files in the runfiles tree. These are created in every directory containing Python source code or shared libraries, and every parent directory of those directories, excluding the repo root directory. The default, -1 (auto), means true unless --incompatible\_default\_to\_explicit\_init\_py is used. If false, the user is responsible for creating (possibly empty) \_\_init\_\_.py files and adding them to the srcs of Python targets as required.
main	Label; default is None Optional; the name of the source file that is the main entry point of the application. This file must also be listed in srcs. If left unspecified, name, with .py appended, is used instead. If name does not match any filename in srcs, main must be specified.
precompile	String; default is "inherit" Whether py source files **for this target** should be precompiled. Values: * inherit: Allow the downstream binary decide if precompiled files are used. * enabled: Compile Python source files at build time. * disabled: Don’t compile Python source files at build time. ::: * The --precompile flag, which can override this attribute in some cases and will affect all targets when building. * The pyc\_collection attribute for transitively enabling precompiling on a per-target basis. * The Precompiling docs for a guide about using precompiling. :::
precompile_invalidation_mode	String; default is "auto" How precompiled files should be verified to be up-to-date with their associated source files. Possible values are: * auto: The effective value will be automatically determined by other build settings. * checked\_hash: Use the pyc file if the hash of the source file matches the hash recorded in the pyc file. This is most useful when working with code that you may modify. * unchecked\_hash: Always use the pyc file; don’t check the pyc’s hash against the source file. This is most useful when the code won’t be modified. For more information on pyc invalidation modes, see https://docs.python.org/3/library/py\_compile.html#py\_compile.PycInvalidationMode
precompile_optimize_level	Integer; default is 0 The optimization level for precompiled files. For more information about optimization levels, see the compile() function’s optimize arg docs at https://docs.python.org/3/library/functions.html#compile NOTE: The value -1 means “current interpreter”, which will be the interpreter used _at build time when pycs are generated_, not the interpreter used at runtime when the code actually runs.
precompile_source_retention	String; default is "inherit" Determines, when a source file is compiled, if the source file is kept in the resulting output or not. Valid values are: * inherit: Inherit the value from the --precompile\_source\_retention flag. * keep\_source: Include the original Python source. * omit\_source: Don’t include the original py source.
pyc_collection	String; default is "inherit" Determines whether pyc files from dependencies should be manually included. Valid values are: * inherit: Inherit the value from --precompile. * include\_pyc: Add implicitly generated pyc files from dependencies. i.e. pyc files for targets that specify precompile="inherit". * disabled: Don’t add implicitly generated pyc files. Note that pyc files may still come from dependencies that enable precompiling at the target level.
python_version	String; default is "PY3" Defunct, unused, does nothing.
srcs_version	String; default is "PY2AND3" Defunct, unused, does nothing.
stamp	Integer; default is 0 Whether to encode build information into the binary. Possible values: * stamp = 1: Always stamp the build information into the binary, even in --nostamp builds. **This setting should be avoided**, since it potentially kills remote caching for the binary and any downstream actions that depend on it. * stamp = 0: Always replace build information by constant values. This gives good build result caching. * stamp = -1: Embedding of build information is controlled by the --[no]stamp flag. Stamped binaries are not rebuilt unless their dependencies change. WARNING: Stamping can harm build performance by reducing cache hits and should be avoided if possible.

py_runtime

View rule sourceopen_in_new

py_runtime(name, abi_flags, bootstrap_template, compatible_with, coverage_tool, deprecation, distribs, exec_compatible_with, exec_properties, features, files, implementation_name, interpreter, interpreter_path, interpreter_version_info, pyc_tag, python_version, restricted_to, stage2_bootstrap_template, stub_shebang, tags, target_compatible_with, testonly, toolchains, visibility, zip_main_template)

Represents a Python runtime used to execute Python code. A py\_runtime target can represent either a *platform runtime* or an *in-build runtime*. A platform runtime accesses a system-installed interpreter at a known path, whereas an in-build runtime points to an executable target that acts as the interpreter. In both cases, an “interpreter” means any executable binary or wrapper script that is capable of running a Python script passed on the command line, following the same conventions as the standard CPython interpreter. A platform runtime is by its nature non-hermetic. It imposes a requirement on the target platform to have an interpreter located at a specific path. An in-build runtime may or may not be hermetic, depending on whether it points to a checked-in interpreter or a wrapper script that accesses the system interpreter. Example

load("@rules\_python//python:py\_runtime.bzl", "py\_runtime")
py\_runtime(
name = "python-2.7.12",
files = glob(["python-2.7.12/\*\*"]),
interpreter = "python-2.7.12/bin/python",
)
py\_runtime(
name = "python-3.6.0",
interpreter\_path = "/opt/pyenv/versions/3.6.0/bin/python",
)

Arguments

Attributes
name	Name; required A unique name for this target.
abi_flags	String; default is "" The runtime’s ABI flags, i.e. sys.abiflags. If not set, then it will be set based on flags.
bootstrap_template	Label; default is "@rules_python//python/private:bootstrap_template" The bootstrap script template file to use. Should have %python_binary%, %workspace_name%, %main%, and %imports%. This template, after expansion, becomes the executable file used to start the process, so it is responsible for initial bootstrapping actions such as finding the Python interpreter, runfiles, and constructing an environment to run the intended Python application. While this attribute is currently optional, it will become required when the Python rules are moved out of Bazel itself. The exact variable names expanded is an unstable API and is subject to change. The API will become more stable when the Python rules are moved out of Bazel itself. See @bazel_tools//tools/python:python_bootstrap_template.txt for more variables.
coverage_tool	Label; default is None This is a target to use for collecting code coverage information from py\_binary and py\_test targets. If set, the target must either produce a single file or be an executable target. The path to the single file, or the executable if the target is executable, determines the entry point for the python coverage tool. The target and its runfiles will be added to the runfiles when coverage is enabled. The entry point for the tool must be loadable by a Python interpreter (e.g. a .py or .pyc file). It must accept the command line arguments of coverage.py, at least including the run and lcov subcommands.
files	List of labels; default is [] For an in-build runtime, this is the set of files comprising this runtime. These files will be added to the runfiles of Python binaries that use this runtime. For a platform runtime this attribute must not be set.
implementation_name	String; default is "cpython" The Python implementation name (sys.implementation.name)
interpreter	Label; default is None For an in-build runtime, this is the target to invoke as the interpreter. It can be either of: * A single file, which will be the interpreter binary. It’s assumed such interpreters are either self-contained single-file executables or any supporting files are specified in files. * An executable target. The target’s executable will be the interpreter binary. Any other default outputs (target.files) and plain files runfiles (runfiles.files) will be automatically included as if specified in the files attribute. NOTE: the runfiles of the target may not yet be properly respected/propagated to consumers of the toolchain/interpreter, see bazelbuild/rules_python/issues/1612 For a platform runtime (i.e. interpreter\_path being set) this attribute must not be set.
interpreter_path	String; default is "" For a platform runtime, this is the absolute path of a Python interpreter on the target platform. For an in-build runtime this attribute must not be set.
interpreter_version_info	Dictionary: String -> String; default is {} Version information about the interpreter this runtime provides. If not specified, uses --python\_version The supported keys match the names for sys.version\_info. While the input values are strings, most are converted to ints. The supported keys are: * major: int, the major version number * minor: int, the minor version number * micro: optional int, the micro version number * releaselevel: optional str, the release level * serial: optional int, the serial number of the release ::: 0.36.0 --python\_version determines the default value. :::
pyc_tag	String; default is "" Optional string; the tag portion of a pyc filename, e.g. the cpython-39 infix of foo.cpython-39.pyc. See PEP 3147. If not specified, it will be computed from implementation\_name and interpreter\_version\_info. If no pyc_tag is available, then only source-less pyc generation will function correctly.
python_version	String; default is "PY3" Whether this runtime is for Python major version 2 or 3. Valid values are "PY2" and "PY3". The default value is controlled by the --incompatible\_py3\_is\_default flag. However, in the future this attribute will be mandatory and have no default value.
stage2_bootstrap_template	Label; default is "@rules_python//python/private:stage2_bootstrap_template" The template to use when two stage bootstrapping is enabled ::: PyRuntimeInfo.stage2\_bootstrap\_template and --bootstrap\_impl :::
stub_shebang	String; default is "#!/usr/bin/env python3" “Shebang” expression prepended to the bootstrapping Python stub script used when executing py\_binary targets. See https://github.com/bazelbuild/bazel/issues/8685 for motivation. Does not apply to Windows.
zip_main_template	Label; default is "@rules_python//python/private:zip_main_template" The template to use for a zip’s top-level \_\_main\_\_.py file. This becomes the entry point executed when python foo.zip is run. ::: The PyRuntimeInfo.zip\_main\_template field. :::