Context Informants

Context informants tell the ContextManager about the context.

Each informant provides a unique string for each individual context. The context manager then caches objects by context. The context should be destroyed when it is no longer needed.

class autoinject.informants.ContextVarInformant

Context informant for contextvars library.

destroy_self(context: ContextProtocol | Context | None = None)

Destroy the context related to the contextvars context passed or the current one if None.

get_cache_id() → str

Obtain the current context ID from the contextvars.

class autoinject.informants.ContextVarManager(contextvar_informant: ContextVarInformant, context: Literal['_default', 'same', 'empty', 'copy'] | ContextProtocol | Context | None = '_default', suppress_exit_warning: bool = False)

Wrapper around contexts to help manage issues with cleaning up dependencies.

copy(same_autoinject_context: bool = False)

Make a copy of the context, with optional parameter to keep or reset the autoinjection variables.

static ensure_context_id(context: ContextProtocol | Context | None = None)

Ensure there is a context ID.

static freshen_context(context: ContextProtocol | Context | None = None) → Token

Refresh the context by resetting the context ID.

static get_context_id(context: ContextProtocol | Context | None = None) → str | None

Retrieve the current context ID, but don’t set one if there isn’t one.

reset(var: ContextVar, token: Any)

Reset a variable.

static restore_context_id(token, context: ContextProtocol | Context | None = None)

Refresh the context by resetting the context ID.

run(cmd: Callable[[...], Q], *args, **kwargs) → Q

Run, in context if appropriate.

set(var: ContextVar, value: Any)

Set a variable and return a token

class autoinject.informants.NamedSituationInformant(name: str = 'named_situation')

A toy class for demonstrating how contexts work. The context can be changed using switch_context():

from autoinject import injector, NamedContextInformant

informant = NamedContextInformant()
injector.register_informant(informant)
# We are now in the "_default" context
informant.switch_context("alpha")
# We are now in the "alpha" context

In the above example, any calls to inject classes registered with a cache strategy of CONTEXT_CACHE (the default) will result in different obtains being returned for the _default context and the alpha context. If the class is registered with a strategy of GLOBAL_CACHE, the same object will be returned.

destroy_self()

Destroy the current context

get_cache_id() → str

Provide the context ID to the ContextManager

switch_context(cache_id: str)

Change the context ID

class autoinject.informants.SituationInformant(name: str | None = None)

Base class for context informants

Parameters:

name (str) – A unique name for this informant. It will be used to assemble multiple contexts together.

check_expired_caches()

Trigger to check for expired contexts so they can be cleaned-up from memory

destroy(cache_id: str)

Remove all objects cached under the given context.

Parameters:

cache_id (str) – A value that would have been provided by get_context_id() to the ContextManager

abstractmethod get_cache_id() → str

Obtains a unique identifier for the current context. This is paired with the informant name to create a

unique string for each context.

Returns:

A unique string per context

Return type:

str

set_cache_manager(cache_manager: autoinject.cache_manager.CacheManager)

Set the context manager. This is called by the ContextManager when the informant is registered.

Parameters:

cache_manager (autoinject.cache_manager.CacheManager) – The context manager

class autoinject.informants.ThreadedContextInformant

Context informant for threading library

check_expired_caches()

Since threads don’t reliably have a callback when they complete, we instead regularly monitor the active thread list and remove them as they complete to cut down on memory usage.

destroy_self(thread: Thread | None = None)

Destroy the current thread context.

get_cache_id()

Provide the context ID to the ContextManager