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)

pluggy 0.13.0 (2019-09-10)

pluggy 0.12.0 (2019-05-27)

pluggy 0.11.0 (2019-05-07)

pluggy 0.10.0 (2019-05-07)

pluggy 0.9.0 (2019-02-21)

pluggy 0.8.1 (2018-11-09)

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