A definitive example

import pluggy

hookspec = pluggy.HookspecMarker("myproject")
hookimpl = pluggy.HookimplMarker("myproject")


class MySpec(object):
    """A hook specification namespace.
    """

    @hookspec
    def myhook(self, arg1, arg2):
        """My special little hook that you can customize.
        """


class Plugin_1(object):
    """A hook implementation namespace.
    """

    @hookimpl
    def myhook(self, arg1, arg2):
        print("inside Plugin_1.myhook()")
        return arg1 + arg2


class Plugin_2(object):
    """A 2nd hook implementation namespace.
    """

    @hookimpl
    def myhook(self, arg1, arg2):
        print("inside Plugin_2.myhook()")
        return arg1 - arg2


# create a manager and add the spec
pm = pluggy.PluginManager("myproject")
pm.add_hookspecs(MySpec)

# register plugins
pm.register(Plugin_1())
pm.register(Plugin_2())

# call our ``myhook`` hook
results = pm.hook.myhook(arg1=1, arg2=2)
print(results)

Running this directly gets us:

$ python docs/examples/toy-example.py
inside Plugin_2.myhook()
inside Plugin_1.myhook()
[-1, 3]

pluggy 0.13.1 (2019-11-21)

Trivial/Internal Changes

• #236: Improved documentation, especially with regard to references.

pluggy 0.13.0 (2019-09-10)

Trivial/Internal Changes

• #222: Replace importlib_metadata backport with importlib.metadata from the standard library on Python 3.8+.

pluggy 0.12.0 (2019-05-27)

Features

• #215: Switch from pkg_resources to importlib-metadata for entrypoint detection for improved performance and import time. This time with .egg support.

pluggy 0.11.0 (2019-05-07)

Bug Fixes

• #205: Revert changes made in 0.10.0 release breaking .egg installs.

pluggy 0.10.0 (2019-05-07)

Features

• #199: Switch from pkg_resources to importlib-metadata for entrypoint detection for improved performance and import time.

pluggy 0.9.0 (2019-02-21)

pluggy 0.8.1 (2018-11-09)

Trivial/Internal Changes

• #166: Add stacklevel=2 to implprefix warning so that the reported location of warning is the caller of PluginManager.

pluggy 0.8.0 (2018-10-15)

pluggy 0.7.1 (2018-07-28)

pluggy 0.7.0 (Unreleased)

• #160: We discovered a deployment issue so this version was never released to PyPI, only the tag exists.

pluggy 0.6.0 (2017-11-24)

• Add CI testing for the features, release, and master branches of pytest (PR #79).
• Document public API for _Result objects passed to wrappers (PR #85).
• Document and test hook LIFO ordering (PR #85).
• Turn warnings into errors in test suite (PR #89).
• Deprecate _Result.result (PR #88).
• Convert _Multicall to a simple function distinguishing it from the legacy version (PR #90).
• Resolve E741 errors (PR #96).
• Test and bug fix for unmarked hook collection (PRs #97 and #102).
• Drop support for EOL Python 2.6 and 3.3 (PR #103).
• Fix inspect based arg introspection on py3.6 (PR #94).

pluggy 0.5.2 (2017-09-06)

• fix bug where firstresult wrappers were being sent an incorrectly configured _Result (a list was set instead of a single value). Add tests to check for this as well as _Result.force_result() behaviour. Thanks to @tgoodlet for the PR #72.
• fix incorrect getattr of DeprecationWarning from the warnings module. Thanks to @nicoddemus for the PR #77.
• hide pytest tracebacks in certain core routines. Thanks to @nicoddemus for the PR #80.

pluggy 0.5.1 (2017-08-29)

• fix a bug and add tests for case where firstresult hooks return None results. Thanks to @RonnyPfannschmidt and @tgoodlet for the issue (#68) and PR (#69) respectively.

pluggy 0.5.0 (2017-08-28)

• fix bug where callbacks for historic hooks would not be called for already registered plugins. Thanks @vodik for the PR and @hpk42 for further fixes.
• fix #17 by considering only actual functions for hooks this removes the ability to register arbitrary callable objects which at first glance is a reasonable simplification, thanks @RonnyPfannschmidt for report and pr.
• fix #19: allow registering hookspecs from instances. The PR from @tgoodlet also modernized the varnames implementation.
• resolve #32: split up the test set into multiple modules. Thanks to @RonnyPfannschmidt for the PR and @tgoodlet for the initial request.
• resolve #14: add full sphinx docs. Thanks to @tgoodlet for PR #39.
• add hook call mismatch warnings. Thanks to @tgoodlet for the PR #42.
• resolve #44: move to new-style classes. Thanks to @MichalTHEDUDE for PR #46.
• add baseline benchmarking/speed tests using pytest-benchmark in PR #54. Thanks to @tgoodlet.
• update the README to showcase the API. Thanks to @tgoodlet for the issue and PR #55.
• deprecate __multicall__ and add a faster call loop implementation. Thanks to @tgoodlet for PR #58.
• raise a comprehensible error when a hookimpl is called with positional args. Thanks to @RonnyPfannschmidt for the issue and @tgoodlet for PR #60.
• fix the firstresult test making it more complete and remove a duplicate of that test. Thanks to @tgoodlet for PR #62.

pluggy 0.4.0 (2016-09-25)

• add has_plugin(name) method to pluginmanager. thanks @nicoddemus.
• fix #11: make plugin parsing more resilient against exceptions from __getattr__ functions. Thanks @nicoddemus.
• fix issue #4: specific HookCallError exception for when a hook call provides not enough arguments.
• better error message when loading setuptools entrypoints fails due to a VersionConflict. Thanks @blueyed.

pluggy 0.3.1 (2015-09-17)

• avoid using deprecated-in-python3.5 getargspec method. Thanks @mdboom.

pluggy 0.3.0 (2015-05-07)

initial release