API Reference

PluginManager	Core class which manages registration of plugin objects and hook calls.
HookCaller	The primary hook-calling object.
HookResult	A class to store/modify results from a _multicall() hook loop.
HookImplementation	A class to encapsulate hook implementations.
HookSpecification	A class to encapsulate hook specifications.
HookSpecificationMarker	Decorator helper class for marking functions as hook specifications.
HookImplementationMarker	Decorator helper class for marking functions as hook implementations.

PluginManager

class napari_plugin_engine.PluginManager(project_name, *, discover_entry_point=None, discover_prefix=None, discover_path=None)

Core class which manages registration of plugin objects and hook calls.

You can register new hooks by calling add_hookspecs(). You can register plugin objects (which contain hooks) by calling register(). The PluginManager is initialized with a project_name that is used when discovering hook specifications and hook implementations.

For debugging purposes you may call PluginManager.enable_tracing() which will subsequently send debug information to the trace helper.

Parameters

• project_name (str) – The name of the host project. All HookImplementationMarker and HookSpecificationMarker instances must be created using the same project_name to be detected by this plugin manager.

• discover_entry_point (str, optional) – The default entry_point group to search when discovering plugins with PluginManager.discover(), by default None

• discover_prefix (str, optional) – The default module prefix to use when discovering plugins with PluginManager.discover(), by default None

• discover_path (str or list of str, optional) – A path or paths to include when discovering plugins with PluginManager.discover(), by default None

Examples

from napari_plugin_engine import PluginManager
import my_hookspecs

plugin_manager = PluginManager(
    'my_project',
    discover_entry_point='app.plugin',
    discover_prefix='app_',
)
plugin_manager.add_hookspecs(my_hookspecs)
plugin_manager.discover()

# hooks now live in plugin_manager.hook
# plugin dict is at plugin_manager.plugins

_ensure_plugin(name_or_object)

Return plugin object given a name or object. Or raise an exception.

Parameters

name_or_object (Any) – Either a string (in which case it is interpreted as a plugin name), or a non-string object (in which case it is assumed to be a plugin module or class).

Returns

The plugin object, if found.

Return type

Any

Raises

KeyError – If the plugin does not exist.

_hookexec(caller, methods, kwargs)

Returns a function that will call a set of hookipmls with a caller.

This function will be passed to HookCaller instances that are created during hookspec and plugin registration.

If enable_tracing() is used, it will set it’s own wrapper function at self._inner_hookexec to enable tracing of hook calls.

Parameters

• caller (HookCaller) – The HookCaller instance that will call the HookImplementations.

• methods (List[HookImplementation]) – A list of HookImplementation objects whose functions will be called during the hook call loop.

• kwargs (dict) – Keyword arguments to pass when calling the HookImplementation.

Returns

The result object produced by the multicall loop.

Return type

HookResult

_plugin2hookcallers: Dict[Any, List[HookCaller]] = None

mapping of plugin (object) → list of HookCaller

HookCaller s get added in register()

Type

dict

_register_dict(dct, name=None, **kwargs)

Register a dict as a mapping of method name -> method.

Parameters

• dct (Dict[str, Callable]) – Mapping of method name to method.

• name (Optional[str], optional) – The plugin_name to assign to this object, by default None

Returns

canonical plugin name, or None if the name is blocked from registering.

Return type

str or None

_verify_hook(hook_caller, hookimpl)

Check validity of a hookimpl

Parameters

• hook_caller (HookCaller) – A HookCaller instance.

• hookimpl (HookImplementation) – A HookImplementation instance, implementing the hook in hook_caller.

Raises

• PluginValidationError – If hook_caller is historic and the hookimpl is a hookwrapper.

• PluginValidationError – If there are any argument names in the hookimpl that are not in the hook_caller.spec.

Warns

Warning – If the hookspec has warn_on_impl flag (usually a deprecation).

add_hookcall_monitoring(before, after)

Add before/after tracing functions for all hooks.

return an undo function which, when called, will remove the added tracers.

before(hook_name, hook_impls, kwargs) will be called ahead of all hook calls and receive a hookcaller instance, a list of HookImplementation instances and the keyword arguments for the hook call.

after(outcome, hook_name, hook_impls, kwargs) receives the same arguments as before but also a napari_plugin_engine.callers._Result object which represents the result of the overall hook call.

Return type

Callable[[], None]

add_hookspecs(namespace)

Add new hook specifications defined in the given namespace.

Functions are recognized if they have been decorated accordingly.

check_pending()

Make sure all hooks have a specification, or are optional.

Raises

PluginValidationError – If a hook implementation that was not marked as optionalhook has been registered for a non-existent hook specification.

discover(path=None, entry_point=None, prefix=None, ignore_errors=True)

Discover and load plugins.

Parameters

• path (str, optional) – If a string is provided, it is added to sys.path (and self.discover_path) before importing, and removed at the end.

• entry_point (str, optional) – An entry_point group to search for, by default self.discover_entry_point is used

• prefix (str, optional) – If provided, modules in the environment starting with prefix will be imported and searched for hook implementations by default self.discover_prefix is used

• ignore_errors (bool, optional) – If True, errors will be gathered and returned at the end. Otherwise, they will be raised immediately. by default True

Returns

(count, errs) – The number of succefully loaded modules, and a list of errors that occurred (if ignore_errors was True)

Return type

Tuple[int, List[PluginError]]

discovery_blocked()

A context manager that temporarily blocks discovery of new plugins.

Return type

Generator

enable_tracing()

Enable tracing of hook calls and return an undo function.

get_errors(plugin=<Empty.token: 0>, error_type=<Empty.token: 0>)

Return a list of PluginErrors associated with plugin.

Parameters

• plugin (Any) – If provided, will restrict errors to those that were raised by plugin. If a string is provided, it will be interpreted as the name of the plugin, otherwise it is assumed to be the actual plugin object itself.

• error_type (PluginError) – If provided, will restrict errors to instances of error_type.

Return type

List[PluginError]

get_hookcallers(plugin)

get all hook callers for the specified plugin.

Return type

Optional[List[HookCaller]]

get_metadata(plugin, *values)

Return metadata values for a given plugin

Parameters

• plugin (Any) – Either a string (in which case it is interpreted as a plugin name), or a non-string object (in which case it is assumed to be a plugin module or class).

• *values (str) – key(s) to lookup in the plugin object distribution metadata. At least one value must be supplied.

Raises

• TypeError – If no values are supplied.

• KeyError – If the plugin does not exist.

Return type

Union[str, Dict[str, Optional[str]], None]

get_name(plugin)

Return name for registered plugin or None if not registered.

get_standard_metadata(plugin)

Return a standard metadata dict for plugin.

Parameters

plugin (Any) – A plugin name or any object. If it is a plugin name, it must be a registered plugin.

Returns

metadata – A dicts with plugin metadata. The dict is guaranteed to have the following keys:

• plugin_name: The name of the plugin as registered

• package: The name of the package

• version: The version of the plugin package

• summary: A one-line summary of what the distribution does

• author: The author’s name

• email: The author’s (or maintainer’s) e-mail address.

• license: The license covering the distribution

• url: The home page for the package, or dowload url if N/A.

• hooks: A list of hookspec names that this plugin implements.

Return type

dict

Raises

KeyError – If plugin is a string, but is not a registered plugin_name.

property hooks

An alias for PluginManager.hook

Return type

_HookRelay

is_blocked(plugin_name)

Return True if the given plugin name is blocked.

Return type

bool

is_registered(obj)

Return True if the plugin is already registered.

Return type

bool

iter_available(path=None, entry_point=None, prefix=None)

Iterate over available plugins.

Parameters

• path (str, optional) – If a string is provided, it is added to sys.path (and self.discover_path) before importing, and removed at the end.

• entry_point (str, optional) – An entry_point group to search for, by default self.discover_entry_point is used

• prefix (str, optional) – If provided, modules in the environment starting with prefix will be imported and searched for hook implementations by default self.discover_prefix is used

Notes

See docstring of iter_available_plugins() for details.

Return type

Generator[Tuple[str, str, Optional[str]], None, None]

list_plugin_metadata()

Return list of standard metadata dicts for every registered plugin.

Returns

metadata – A list of dicts with plugin metadata. Every dict in the list is guaranteed to have the following keys mentioned in get_standard_metadata()

Return type

dict

plugins: Dict[str, Any] = None

mapping of plugin_name → plugin (object)

Plugins get added to this dict in register()

Type

dict

prune()

Unregister modules that can no longer be imported.

Useful if pip uninstall has been run during the session.

register(namespace, name=None)

Register a plugin and return its canonical name or None.

Parameters

• namespace (Any) – The namespace (class, module, dict, etc…) of the plugin to register

• name (str, optional) – Optional name for plugin, by default get_canonical_name(plugin)

Returns

canonical plugin name, or None if the name is blocked from registering.

Return type

str or None

Raises

• TypeError – If namespace is a string.

• ValueError – if the plugin name or namespace is already registered.

set_blocked(plugin_name, blocked=True)

Block registrations of plugin_name, unregister if registered.

Parameters

• plugin_name (str) – A plugin name to block.

• blocked (bool, optional) – Whether to block the plugin. If False will “unblock” plugin_name. by default True

unregister(name_or_object)

Unregister a plugin object or plugin_name.

Parameters

name_or_object (str or Any) – A module/class object or a plugin name (string).

Returns

module – The module object, or None if the name_or_object was not found.

Return type

Any or None

HookCaller

class napari_plugin_engine.HookCaller(name, hook_execute, namespace=None, spec_opts=None)

The primary hook-calling object.

A PluginManager may have multiple HookCaller objects and they are stored in the plugin_manager.hook namespace, named after the hook specification that they represent. For instance:

pm = PluginManager("demo")
pm.add_hookspec(some_module)
# assuming `some_module` had an @hookspec named `my specification`
assert isinstance(pm.hook.my_specification, HookCaller)

Each HookCaller instance stores all of the HookImplementation objects discovered during plugin registration (each of which capture the implementation of a specific plugin for this hook specification).

The HookCaller instance also usually creates and stores a reference to the HookSpecification instance that encapsulates information about the hook specification, (at HookCaller.spec)

Parameters

• name (str) – The name of the hook specification that this HookCaller represents.

• hook_execute (Callable) – A HookExecFunc function. In almost every case, this will be provided by the PluginManager during hook registration as PluginManager._hookexec()… which is, in turn, mostly just a wrapper around _multicall().

• namespace (Any, optional) – An namespace (such as a module or class) to search during HookSpecification creation for functions decorated with @hookspec named with the string name.

• spec_opts (Optional[dict], optional) – keyword arguments to be passed when creating the HookSpecification instance at self.spec.

__call__(*args, _plugin=None, _skip_impls=[], **kwargs)

Call hook implementation(s) for this spec and return result(s).

This is the primary way to call plugin hook implementations.

Note

Parameters are prefaced by underscores to reduce potential conflicts with argument names in hook specifications. There is a test in test_hook_specifications.test_annotation_on_hook_specification() to ensure that these argument names are never used in one of our hookspecs.

Parameters

• _plugin (str, optional) – The name of a specific plugin to use. By default all implementations will be called (though if firstresult==True, only the first non-None result will be returned).

• _skip_impls (List[HookImplementation], optional) – A list of HookImplementation instances that should be skipped when calling hook implementations, by default None

• **kwargs – keys should match the names of arguments in the corresponding hook specification, values will be passed as arguments to the hook implementations.

Raises

• HookCallError – If one or more of the keys in kwargs is not present in one of the hook_impl.argnames.

• PluginCallError – If firstresult == True and a plugin raises an Exception.

Returns

If the hookspec was declared with firstresult==True, a single result will be returned. Otherwise will return a list of results from all hook implementations for this hook caller.

If _plugin is provided, will return the single result from the specified plugin.

Return type

result

_add_hookimpl(hookimpl)

Add an implementation to the callback chain.

_call_plugin(plugin_name, *args, **kwargs)

Call the hook implementation for a specific plugin

Note

This method is not intended to be called directly. Instead, just call the instance directly, specifing the _plugin argument. See the __call__() method.

Parameters

plugin_name (str) – Name of the plugin

Returns

Result of implementation call provided by plugin

Return type

Any

Raises

• TypeError – If the implementation is a hook wrapper (cannot be called directly)

• TypeError – If positional arguments are provided

• HookCallError – If one of the required arguments in the hook specification is not present in kwargs.

• PluginCallError – If an exception is raised when calling the plugin

_set_plugin_enabled(plugin_name, enabled)

Enable or disable the hook implementation for a specific plugin.

Parameters

• plugin_name (str) – The name of a plugin implementing hook_spec.

• enabled (bool) – Whether or not the implementation should be enabled.

Raises

KeyError – If plugin_name has not provided a hook implementation for this hook specification.

bring_to_front(new_order)

Move items in new_order to the front of the call order.

By default, hook implementations are called in last-in-first-out order of registration, and pluggy does not provide a built-in way to rearrange the call order of hook implementations.

This function accepts a HookCaller instance and the desired new_order of the hook implementations (in the form of list of plugin names, or a list of actual HookImplementation instances) and reorders the implementations in the hook caller accordingly.

Note

Hook implementations are actually stored in two separate list attributes in the hook caller: HookCaller._wrappers and HookCaller._nonwrappers, according to whether the corresponding HookImplementation instance was marked as a wrapper or not. This method only sorts _nonwrappers.

Parameters

new_order (list of str or list of HookImplementation) – instances The desired CALL ORDER of the hook implementations. The list does not need to include every hook implementation in get_hookimpls(), but those that are not included will be left at the end of the call order.

Raises

• TypeError – If any item in new_order is neither a string (plugin_name) or a HookImplementation instance.

• ValueError – If any item in new_order is neither the name of a plugin or a HookImplementation instance that is present in self._nonwrappers.

• ValueError – If new_order argument has multiple entries for the same implementation.

Examples

Imagine you had a hook specification named print_plugin_name, that expected plugins to simply print their own name. An implementation might look like:

>>> # hook implementation for ``plugin_1``
>>> @hook_implementation
... def print_plugin_name():
...     print("plugin_1")

If three different plugins provided hook implementations. An example call for that hook might look like:

>>> plugin_manager.hook.print_plugin_name()
plugin_1
plugin_2
plugin_3

If you wanted to rearrange their call order, you could do this:

>>> new_order = ["plugin_2", "plugin_3", "plugin_1"]
>>> plugin_manager.hook.print_plugin_name.bring_to_front(new_order)
>>> plugin_manager.hook.print_plugin_name()
plugin_2
plugin_3
plugin_1

You can also just specify one or more item to move them to the front of the call order: >>> plugin_manager.hook.print_plugin_name.bring_to_front([“plugin_3”]) >>> plugin_manager.hook.print_plugin_name() plugin_3 plugin_2 plugin_1

call_extra(methods, kwargs)

Call the hook with some additional temporarily participating methods using the specified kwargs as call parameters.

call_historic(result_callback=None, kwargs=None, with_impl=False)

Call the hook with given kwargs for all registered plugins and for all plugins which will be registered afterwards.

If result_callback is not None it will be called for for each non-None result obtained from a hook implementation.

If with_impl is True, the caller is indicating that result_callback has a signature of callback(result, hookimpl), and will be called as such.

call_with_result_obj(*, _skip_impls=[], **kwargs)

Call hook implementation(s) for this spec and return HookResult.

The HookResult object carries the result (in its result property) but also additional information about the hook call, such as the implementation that returned each result and any call errors.

Parameters

• _skip_impls (List[HookImplementation], optional) – A list of HookImplementation instances that should be skipped when calling hook implementations, by default None

• **kwargs – keys should match the names of arguments in the corresponding hook specification, values will be passed as arguments to the hook implementations.

Returns

result – A HookResult object that contains the results returned by plugins along with other metadata about the call.

Return type

HookResult

Raises

• HookCallError – If one or more of the keys in kwargs is not present in one of the hook_impl.argnames.

• PluginCallError – If firstresult == True and a plugin raises an Exception.

disable_plugin(plugin_name)

disable implementation for plugin_name.

enable_plugin(plugin_name)

enable implementation for plugin_name.

get_plugin_implementation(plugin_name)

Return hook implementation instance for plugin_name if found.

index(value)

Return index of plugin_name or a HookImplementation in self._nonwrappers

Return type

int

HookResult

class napari_plugin_engine.HookResult(result, excinfo, firstresult=False, plugin_errors=None)

A class to store/modify results from a _multicall() hook loop.

Results are accessed in .result property, which will also raise any exceptions that occured during the hook loop.

Parameters

• results (List[Tuple[Any, HookImplementation]]) – A list of (result, HookImplementation) tuples, with the result and HookImplementation object responsible for each result collected during a _multicall loop.

• excinfo (tuple) – The output of sys.exc_info() if raised during the multicall loop.

• firstresult (bool, optional) – Whether the hookspec had firstresult == True, by default False. If True, self._result, and self.implementation will be single values, otherwise they will be lists.

• plugin_errors (list) – A list of any PluginCallError instances that were created during the multicall loop.

force_result(result)

Force the result(s) to result.

This may be used by hookwrappers to alter this result object.

If the hook was marked as a firstresult a single value should be set otherwise set a (modified) list of results. Any exceptions found during invocation will be deleted.

classmethod from_call(func)

Used when hookcall monitoring is enabled.

https://pluggy.readthedocs.io/en/latest/#call-monitoring

implementation: Optional[Union[HookImplementation, List[HookImplementation]]] = None

The HookImplementation(s) that were responsible for each result in result

is_firstresult: bool = None

Whether this HookResult came from a firstresult multicall.

property result

Return the result(s) for this hook call.

If the hook was marked as a firstresult only a single value will be returned otherwise a list of results.

Return type

Union[Any, List[Any]]

HookSpecification

class napari_plugin_engine.HookSpecification(namespace, name, *, firstresult=False, historic=False, warn_on_impl=None)

A class to encapsulate hook specifications.

HookImplementation

class napari_plugin_engine.HookImplementation(function, plugin=None, plugin_name=None, hookwrapper=False, optionalhook=False, tryfirst=False, trylast=False, specname='', enabled=True)

A class to encapsulate hook implementations.

Decorators & Markers

HookSpecificationMarker

class napari_plugin_engine.HookSpecificationMarker(project_name)

Decorator helper class for marking functions as hook specifications.

You can instantiate it with a project_name to get a decorator. Calling PluginManager.add_hookspecs() later will discover all marked functions if the PluginManager uses the same project_name.

__call__(function=None, firstresult=False, historic=False, warn_on_impl=None)

if passed a function, directly sets attributes on the function which will make it discoverable to PluginManager.add_hookspecs(). If passed no function, returns a decorator which can be applied to a function later using the attributes supplied.

If firstresult is True the 1:N hook call (N being the number of registered hook implementation functions) will stop at I<=N when the I’th function returns a non-None result.

If historic is True calls to a hook will be memorized and replayed on later registered plugins.

HookImplementationMarker

class napari_plugin_engine.HookImplementationMarker(project_name)

Decorator helper class for marking functions as hook implementations.

You can instantiate with a project_name to get a decorator. Calling PluginManager.register() later will discover all marked functions if the PluginManager uses the same project_name.

Parameters

project_name (str) – A namespace for plugin implementations. Implementations decorated with this class will be discovered by PluginManager.register if and only if project_name matches the project_name of the PluginManager.

__call__(function=None, *, hookwrapper=False, optionalhook=False, tryfirst=False, trylast=False, specname='')

Call the marker instance.

If passed a function, directly sets attributes on the function which will make it discoverable to PluginManager.register(). If passed no function, returns a decorator which can be applied to a function later using the attributes supplied.

Parameters

• function (callable, optional) – A function to decorate as a hook implementation, If function is None, this method returns a function that can be used to decorate other functions.

• hookwrapper (bool, optional) – Whether this hook implementation behaves as a hookwrapper. by default False

• optionalhook (bool, optional) – If True, a missing matching hook specification will not result in an error (by default it is an error if no matching spec is found), by default False.

• tryfirst (bool, optional) – If True this hook implementation will run as early as possible in the chain of N hook implementations for a specification, by default False

• trylast (bool, optional) – If True this hook implementation will run as late as possible in the chain of N hook implementations, by default False

• specname (str, optional) – If provided, specname will be used instead of the function name when matching this hook implementation to a hook specification during registration, by default the implementation function name must match the name of the corresponding hook specification.

Returns

If function is not None, will decorate the function with attributes, and return the function. If function is None, will return a decorator that can be used to decorate functions.

Return type

Callable

Exceptions

PluginError	Base class for exceptions relating to plugins.
PluginImportError	Plugin module is unimportable.
PluginRegistrationError	If an unexpected error occurs during registration.
PluginImplementationError	Base class for errors pertaining to a specific hook implementation.
PluginValidationError	When a plugin implementation fails validation.
PluginCallError	Raised when an error is raised when calling a plugin implementation.
HookCallError	If a hook is called incorrectly.

PluginError

class napari_plugin_engine.PluginError(message='', *, plugin=None, plugin_name=None, cause=None)

Bases: Exception

Base class for exceptions relating to plugins.

Parameters

• message (str, optional) – An optional error message, by default ‘’

• namespace (Optional[Any], optional) – The python object that caused the error, by default None

• cause (Exception, optional) – Exception that caused the error. Same as raise * from. by default None

classmethod get(*, plugin=<Empty.token: 0>, plugin_name=<Empty.token: 0>, error_type=<Empty.token: 0>)

Return errors that have been logged, filtered by parameters.

Parameters

• manager (PluginManager, optional) – If provided, will restrict errors to those that are owned by manager.

• plugin_name (str) – If provided, will restrict errors to those that were raised by plugin_name.

• error_type (Exception) – If provided, will restrict errors to instances of error_type.

Returns

A list of PluginErrors that have been instantiated during this session that match the provided parameters.

Return type

list of PluginError

Raises

TypeError – If error_type is provided and is not an exception class.

info()

Return info as would be returned from sys.exc_info().

Return type

Tuple[Type[Exception], Exception, Optional[traceback]]

log(package_info=True, logger=None, level=40)

Log this error with metadata, optionally provide logger and level.

Parameters

• package_info (bool, optional) – If true, will include package metadata in log, by default True

• logger (logging.Logger or str, optional) – A Logger instance or name of a logger to use, by default None

• level (int, optional) – The logging level to use, by default logging.ERROR

PluginImportError

class napari_plugin_engine.PluginImportError(message='', *, plugin=None, plugin_name=None, cause=None)

Bases: napari_plugin_engine.exceptions.PluginError, ImportError

Plugin module is unimportable.

PluginRegistrationError

class napari_plugin_engine.PluginRegistrationError(message='', *, plugin=None, plugin_name=None, cause=None)

Bases: napari_plugin_engine.exceptions.PluginError

If an unexpected error occurs during registration.

PluginImplementationError

class napari_plugin_engine.PluginImplementationError(hook_implementation, msg=None, cause=None)

Bases: napari_plugin_engine.exceptions.PluginError

Base class for errors pertaining to a specific hook implementation.

PluginValidationError

class napari_plugin_engine.PluginValidationError(hook_implementation, msg=None, cause=None)

Bases: napari_plugin_engine.exceptions.PluginImplementationError

When a plugin implementation fails validation.

PluginCallError

class napari_plugin_engine.PluginCallError(hook_implementation, msg=None, cause=None)

Bases: napari_plugin_engine.exceptions.PluginImplementationError

Raised when an error is raised when calling a plugin implementation.

HookCallError

class napari_plugin_engine.HookCallError(message='', *, plugin=None, plugin_name=None, cause=None)

Bases: napari_plugin_engine.exceptions.PluginError

If a hook is called incorrectly.

Usually this results when a HookCaller is called without the appropriate arguments.

Extra Functions

napari_plugin_engine.hooks._multicall(hook_impls, caller_kwargs, firstresult=False)

The primary HookImplementation call loop.

Parameters

• hook_impls (list) – A sequence of hook implementation (HookImplementation) objects

• caller_kwargs (dict) – Keyword:value pairs to pass to each hook_impl.function. Every key in the dict must be present in the argnames property for each hook_impl in hook_impls.

• firstresult (bool, optional) – If True, return the first non-null result found, otherwise, return a list of results from all hook implementations, by default False

Returns

outcome – A HookResult object that contains the results returned by plugins along with other metadata about the call.

Return type

HookResult

Raises

• HookCallError – If one or more of the keys in caller_kwargs is not present in one of the hook_impl.argnames.

• PluginCallError – If firstresult == True and a plugin raises an Exception.

napari_plugin_engine.manager.ensure_namespace(obj, name='orphan')

Convert a dict to an object that provides getattr.

Parameters

• obj (Any) – An object, may be a dict, or a regular namespace object.

• name (str, optional) – A name to use for the new namespace, if created. by default ‘orphan’

Returns

A namespace object. If obj is a dict, creates a new type named name, prepopulated with the key:value pairs from obj. Otherwise, if obj is not a dict, will return the original obj.

Return type

type

Raises

ValueError – If obj is a dict that contains keys that are not valid identifiers.

napari_plugin_engine.manager.temp_path_additions(path)

A context manager that temporarily adds path to sys.path.

Parameters

path (str or list of str) – A path or list of paths to add to sys.path

Yields

sys_path (list of str) – The current sys.path for the context.

Return type

Generator

napari_plugin_engine.dist.get_dist(obj)

Return a importlib.metadata.Distribution for any python object.

Parameters

obj (Any) – A python object. If a string, will be interpreted as a dist name.

Returns

dist – The distribution object for the corresponding package, if found.

Return type

Distribution

Types

napari_plugin_engine.hooks.HookExecFunc = typing.Callable[[ForwardRef('HookCaller'), typing.List[napari_plugin_engine.implementation.HookImplementation], dict], napari_plugin_engine.callers.HookResult]

A function that loops calling a list of HookImplementation s and returns a HookResult.

Parameters

• hook_caller (HookCaller) – a HookCaller instance.

• hook_impls (List[HookImplementation]) – a list of HookImplementation instances to call.

• kwargs (dict) – a mapping of keyword arguments to provide to the implementation.

Returns

result – The HookResult object resulting from the call loop.

Return type

HookResult