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1299 lines (1118 loc) · 39.9 KB
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# SOME DESCRIPTIVE TITLE.
# Copyright (C) 2001 Python Software Foundation
# This file is distributed under the same license as the Python package.
# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
#
# Translators:
# Bhuvansh Kataria, 2026
#
#, fuzzy
msgid ""
msgstr ""
"Project-Id-Version: Python 3.15\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2026-07-31 15:58+0000\n"
"PO-Revision-Date: 2025-09-16 00:01+0000\n"
"Last-Translator: Bhuvansh Kataria, 2026\n"
"Language-Team: Panjabi (Punjabi) (https://app.transifex.com/python-doc/"
"teams/5390/pa/)\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Language: pa\n"
"Plural-Forms: nplurals=2; plural=(n != 1);\n"
msgid ""
":mod:`!contextlib` --- Utilities for :keyword:`!with`\\ -statement contexts"
msgstr ""
msgid "**Source code:** :source:`Lib/contextlib.py`"
msgstr ""
msgid ""
"This module provides utilities for common tasks involving the :keyword:"
"`with` statement. For more information see also :ref:`typecontextmanager` "
"and :ref:`context-managers`."
msgstr ""
msgid "Utilities"
msgstr ""
msgid "Functions and classes provided:"
msgstr ""
msgid ""
"An :term:`abstract base class` for classes that implement :meth:`~object."
"__enter__` and :meth:`~object.__exit__`. A default implementation for :meth:"
"`~object.__enter__` is provided which returns ``self`` while :meth:`~object."
"__exit__` is an abstract method which by default returns ``None``. See also "
"the definition of :ref:`typecontextmanager`."
msgstr ""
msgid ""
"An :term:`abstract base class` for classes that implement :meth:`~object."
"__aenter__` and :meth:`~object.__aexit__`. A default implementation for :"
"meth:`~object.__aenter__` is provided which returns ``self`` while :meth:"
"`~object.__aexit__` is an abstract method which by default returns ``None``. "
"See also the definition of :ref:`async-context-managers`."
msgstr ""
msgid ""
"This function is a :term:`decorator` that can be used to define a factory "
"function for :keyword:`with` statement context managers, without needing to "
"create a class or separate :meth:`~object.__enter__` and :meth:`~object."
"__exit__` methods."
msgstr ""
msgid ""
"While many objects natively support use in with statements, sometimes a "
"resource needs to be managed that isn't a context manager in its own right, "
"and doesn't implement a ``close()`` method for use with ``contextlib."
"closing``."
msgstr ""
msgid ""
"An abstract example would be the following to ensure correct resource "
"management::"
msgstr ""
msgid ""
"from contextlib import contextmanager\n"
"\n"
"@contextmanager\n"
"def managed_resource(*args, **kwds):\n"
" # Code to acquire resource, e.g.:\n"
" resource = acquire_resource(*args, **kwds)\n"
" try:\n"
" yield resource\n"
" finally:\n"
" # Code to release resource, e.g.:\n"
" release_resource(resource)"
msgstr ""
msgid "The function can then be used like this::"
msgstr ""
msgid ""
">>> with managed_resource(timeout=3600) as resource:\n"
"... # Resource is released at the end of this block,\n"
"... # even if code in the block raises an exception"
msgstr ""
msgid ""
"The function being decorated must return a :term:`generator`-iterator when "
"called. This iterator must yield exactly one value, which will be bound to "
"the targets in the :keyword:`with` statement's :keyword:`!as` clause, if any."
msgstr ""
msgid ""
"At the point where the generator yields, the block nested in the :keyword:"
"`with` statement is executed. The generator is then resumed after the block "
"is exited. If an unhandled exception occurs in the block, it is reraised "
"inside the generator at the point where the yield occurred. Thus, you can "
"use a :keyword:`try`...\\ :keyword:`except`...\\ :keyword:`finally` "
"statement to trap the error (if any), or ensure that some cleanup takes "
"place. If an exception is trapped merely in order to log it or to perform "
"some action (rather than to suppress it entirely), the generator must "
"reraise that exception. Otherwise the generator context manager will "
"indicate to the :keyword:`!with` statement that the exception has been "
"handled, and execution will resume with the statement immediately following "
"the :keyword:`!with` statement."
msgstr ""
msgid ""
":deco:`contextmanager` uses :class:`ContextDecorator` so the context "
"managers it creates can be used as decorators as well as in :keyword:`with` "
"statements. When used as a decorator, a new generator instance is implicitly "
"created on each function call (this allows the otherwise \"one-shot\" "
"context managers created by :deco:`contextmanager` to meet the requirement "
"that context managers support multiple invocations in order to be used as "
"decorators)."
msgstr ""
msgid "Use of :class:`ContextDecorator`."
msgstr ""
msgid ""
"Similar to :deco:`~contextlib.contextmanager`, but creates an :ref:"
"`asynchronous context manager <async-context-managers>`."
msgstr ""
msgid ""
"This function is a :term:`decorator` that can be used to define a factory "
"function for :keyword:`async with` statement asynchronous context managers, "
"without needing to create a class or separate :meth:`~object.__aenter__` "
"and :meth:`~object.__aexit__` methods. It must be applied to an :term:"
"`asynchronous generator` function."
msgstr ""
msgid "A simple example::"
msgstr ""
msgid ""
"from contextlib import asynccontextmanager\n"
"\n"
"@asynccontextmanager\n"
"async def get_connection():\n"
" conn = await acquire_db_connection()\n"
" try:\n"
" yield conn\n"
" finally:\n"
" await release_db_connection(conn)\n"
"\n"
"async def get_all_users():\n"
" async with get_connection() as conn:\n"
" return conn.query('SELECT ...')"
msgstr ""
msgid ""
"Context managers defined with :deco:`asynccontextmanager` can be used either "
"as decorators or with :keyword:`async with` statements::"
msgstr ""
msgid ""
"import time\n"
"from contextlib import asynccontextmanager\n"
"\n"
"@asynccontextmanager\n"
"async def timeit():\n"
" now = time.monotonic()\n"
" try:\n"
" yield\n"
" finally:\n"
" print(f'it took {time.monotonic() - now}s to run')\n"
"\n"
"@timeit()\n"
"async def main():\n"
" # ... async code ..."
msgstr ""
msgid ""
"When used as a decorator, a new generator instance is implicitly created on "
"each function call. This allows the otherwise \"one-shot\" context managers "
"created by :deco:`asynccontextmanager` to meet the requirement that context "
"managers support multiple invocations in order to be used as decorators."
msgstr ""
msgid ""
"Async context managers created with :deco:`asynccontextmanager` can be used "
"as decorators."
msgstr ""
msgid ""
"Return a context manager that closes *thing* upon completion of the block. "
"This is basically equivalent to::"
msgstr ""
msgid ""
"from contextlib import contextmanager\n"
"\n"
"@contextmanager\n"
"def closing(thing):\n"
" try:\n"
" yield thing\n"
" finally:\n"
" thing.close()"
msgstr ""
msgid "And lets you write code like this::"
msgstr ""
msgid ""
"from contextlib import closing\n"
"from urllib.request import urlopen\n"
"\n"
"with closing(urlopen('https://www.python.org')) as page:\n"
" for line in page:\n"
" print(line)"
msgstr ""
msgid ""
"without needing to explicitly close ``page``. Even if an error occurs, "
"``page.close()`` will be called when the :keyword:`with` block is exited."
msgstr ""
msgid ""
"Most types managing resources support the :term:`context manager` protocol, "
"which closes *thing* on leaving the :keyword:`with` statement. As such, :"
"func:`!closing` is most useful for third party types that don't support "
"context managers. This example is purely for illustration purposes, as :func:"
"`~urllib.request.urlopen` would normally be used in a context manager."
msgstr ""
msgid ""
"Return an async context manager that calls the ``aclose()`` method of "
"*thing* upon completion of the block. This is basically equivalent to::"
msgstr ""
msgid ""
"from contextlib import asynccontextmanager\n"
"\n"
"@asynccontextmanager\n"
"async def aclosing(thing):\n"
" try:\n"
" yield thing\n"
" finally:\n"
" await thing.aclose()"
msgstr ""
msgid ""
"Significantly, ``aclosing()`` supports deterministic cleanup of async "
"generators when they happen to exit early by :keyword:`break` or an "
"exception. For example::"
msgstr ""
msgid ""
"from contextlib import aclosing\n"
"\n"
"async with aclosing(my_generator()) as values:\n"
" async for value in values:\n"
" if value == 42:\n"
" break"
msgstr ""
msgid ""
"This pattern ensures that the generator's async exit code is executed in the "
"same context as its iterations (so that exceptions and context variables "
"work as expected, and the exit code isn't run after the lifetime of some "
"task it depends on)."
msgstr ""
msgid ""
"Return a context manager that returns *enter_result* from :meth:`~object."
"__enter__`, but otherwise does nothing. It is intended to be used as a stand-"
"in for an optional context manager, for example::"
msgstr ""
msgid ""
"def myfunction(arg, ignore_exceptions=False):\n"
" if ignore_exceptions:\n"
" # Use suppress to ignore all exceptions.\n"
" cm = contextlib.suppress(Exception)\n"
" else:\n"
" # Do not ignore any exceptions, cm has no effect.\n"
" cm = contextlib.nullcontext()\n"
" with cm:\n"
" # Do something"
msgstr ""
msgid "An example using *enter_result*::"
msgstr ""
msgid ""
"def process_file(file_or_path):\n"
" if isinstance(file_or_path, str):\n"
" # If string, open file\n"
" cm = open(file_or_path)\n"
" else:\n"
" # Caller is responsible for closing file\n"
" cm = nullcontext(file_or_path)\n"
"\n"
" with cm as file:\n"
" # Perform processing on the file"
msgstr ""
msgid ""
"It can also be used as a stand-in for :ref:`asynchronous context managers "
"<async-context-managers>`::"
msgstr ""
msgid ""
"async def send_http(session=None):\n"
" if not session:\n"
" # If no http session, create it with aiohttp\n"
" cm = aiohttp.ClientSession()\n"
" else:\n"
" # Caller is responsible for closing the session\n"
" cm = nullcontext(session)\n"
"\n"
" async with cm as session:\n"
" # Send http requests with session"
msgstr ""
msgid ":term:`asynchronous context manager` support was added."
msgstr ""
msgid ""
"Return a context manager that suppresses any of the specified exceptions if "
"they occur in the body of a :keyword:`!with` statement and then resumes "
"execution with the first statement following the end of the :keyword:`!with` "
"statement."
msgstr ""
msgid ""
"As with any other mechanism that completely suppresses exceptions, this "
"context manager should be used only to cover very specific errors where "
"silently continuing with program execution is known to be the right thing to "
"do."
msgstr ""
msgid "For example::"
msgstr ""
msgid ""
"from contextlib import suppress\n"
"\n"
"with suppress(FileNotFoundError):\n"
" os.remove('somefile.tmp')\n"
"\n"
"with suppress(FileNotFoundError):\n"
" os.remove('someotherfile.tmp')"
msgstr ""
msgid "This code is equivalent to::"
msgstr ""
msgid ""
"try:\n"
" os.remove('somefile.tmp')\n"
"except FileNotFoundError:\n"
" pass\n"
"\n"
"try:\n"
" os.remove('someotherfile.tmp')\n"
"except FileNotFoundError:\n"
" pass"
msgstr ""
msgid "This context manager is :ref:`reentrant <reentrant-cms>`."
msgstr ""
msgid ""
"If the code within the :keyword:`!with` block raises a :exc:"
"`BaseExceptionGroup`, suppressed exceptions are removed from the group. Any "
"exceptions of the group which are not suppressed are re-raised in a new "
"group which is created using the original group's :meth:`~BaseExceptionGroup."
"derive` method."
msgstr ""
msgid ""
"``suppress`` now supports suppressing exceptions raised as part of a :exc:"
"`BaseExceptionGroup`."
msgstr ""
msgid ""
"Context manager for temporarily redirecting :data:`sys.stdout` to another :"
"term:`file object`."
msgstr ""
msgid ""
"This tool adds flexibility to existing functions or classes whose output is "
"hardwired to :data:`sys.stdout`."
msgstr ""
msgid ""
"For example, the output of :func:`help` normally is sent to *sys.stdout*. "
"You can capture that output in a string by redirecting the output to an :"
"class:`io.StringIO` object. The replacement stream is returned from the :"
"meth:`~object.__enter__` method and so is available as the target of the :"
"keyword:`with` statement::"
msgstr ""
msgid ""
"with redirect_stdout(io.StringIO()) as f:\n"
" help(pow)\n"
"s = f.getvalue()"
msgstr ""
msgid ""
"To send the output of :func:`help` to a file on disk, redirect the output to "
"a regular file::"
msgstr ""
msgid ""
"with open('help.txt', 'w') as f:\n"
" with redirect_stdout(f):\n"
" help(pow)"
msgstr ""
msgid "To send the output of :func:`help` to *sys.stderr*::"
msgstr ""
msgid ""
"with redirect_stdout(sys.stderr):\n"
" help(pow)"
msgstr ""
msgid ""
"Note that the global side effect on :data:`sys.stdout` means that this "
"context manager is not suitable for use in library code and most threaded "
"applications. It also has no effect on the output of subprocesses. However, "
"it is still a useful approach for many utility scripts."
msgstr ""
msgid ""
"Similar to :func:`~contextlib.redirect_stdout` but redirecting the global :"
"data:`sys.stderr` to another :term:`file object`."
msgstr ""
msgid ""
"Non parallel-safe context manager to change the current working directory. "
"As this changes a global state, the working directory, it is not suitable "
"for use in most threaded or async contexts. It is also not suitable for most "
"non-linear code execution, like generators, where the program execution is "
"temporarily relinquished -- unless explicitly desired, you should not yield "
"when this context manager is active."
msgstr ""
msgid ""
"This is a simple wrapper around :func:`~os.chdir`, it changes the current "
"working directory upon entering and restores the old one on exit."
msgstr ""
msgid ""
"A base class that enables a context manager to also be used as a decorator."
msgstr ""
msgid ""
"Context managers inheriting from ``ContextDecorator`` have to implement :"
"meth:`~object.__enter__` and :meth:`~object.__exit__` as normal. "
"``__exit__`` retains its optional exception handling even when used as a "
"decorator."
msgstr ""
msgid ""
"``ContextDecorator`` is used by :deco:`contextmanager`, so you get this "
"functionality automatically."
msgstr ""
msgid "Example of ``ContextDecorator``::"
msgstr ""
msgid ""
"from contextlib import ContextDecorator\n"
"\n"
"class mycontext(ContextDecorator):\n"
" def __enter__(self):\n"
" print('Starting')\n"
" return self\n"
"\n"
" def __exit__(self, *exc):\n"
" print('Finishing')\n"
" return False"
msgstr ""
msgid "The class can then be used like this::"
msgstr ""
msgid ""
">>> @mycontext()\n"
"... def function():\n"
"... print('The bit in the middle')\n"
"...\n"
">>> function()\n"
"Starting\n"
"The bit in the middle\n"
"Finishing\n"
"\n"
">>> with mycontext():\n"
"... print('The bit in the middle')\n"
"...\n"
"Starting\n"
"The bit in the middle\n"
"Finishing"
msgstr ""
msgid ""
"This change is just syntactic sugar for any construct of the following form::"
msgstr ""
msgid ""
"def f():\n"
" with cm():\n"
" # Do stuff"
msgstr ""
msgid "``ContextDecorator`` lets you instead write::"
msgstr ""
msgid ""
"@cm()\n"
"def f():\n"
" # Do stuff"
msgstr ""
msgid ""
"It makes it clear that the ``cm`` applies to the whole function, rather than "
"just a piece of it (and saving an indentation level is nice, too)."
msgstr ""
msgid ""
"Existing context managers that already have a base class can be extended by "
"using ``ContextDecorator`` as a mixin class::"
msgstr ""
msgid ""
"from contextlib import ContextDecorator\n"
"\n"
"class mycontext(ContextBaseClass, ContextDecorator):\n"
" def __enter__(self):\n"
" return self\n"
"\n"
" def __exit__(self, *exc):\n"
" return False"
msgstr ""
msgid ""
"As the decorated function must be able to be called multiple times, the "
"underlying context manager must support use in multiple :keyword:`with` "
"statements. If this is not the case, then the original construct with the "
"explicit :keyword:`!with` statement inside the function should be used."
msgstr ""
msgid ""
"When the decorated callable is a generator function, coroutine function, or "
"asynchronous generator function, the returned wrapper is of the same kind "
"and keeps the context manager open for the lifetime of the iteration or "
"await rather than only for the call that creates the generator or coroutine "
"object. Wrapped generators and asynchronous generators are explicitly "
"closed when iteration ends, as if by :func:`closing` or :func:`aclosing`."
msgstr ""
msgid ""
"For asynchronous generators the wrapper re-yields each value with ``async "
"for``; values sent with :meth:`~agen.asend` and exceptions thrown with :meth:"
"`~agen.athrow` are not forwarded to the wrapped generator."
msgstr ""
msgid ""
"Decorating a generator function, coroutine function, or asynchronous "
"generator function now keeps the context manager open across iteration or "
"await. Previously the context manager exited as soon as the generator or "
"coroutine object was created."
msgstr ""
msgid ""
"Similar to :class:`ContextDecorator`, but the context manager is entered and "
"exited with :keyword:`async with`. Decorate coroutine functions and "
"asynchronous generator functions with this class; the returned wrapper is of "
"the same kind."
msgstr ""
msgid ""
"Synchronous functions and generators are accepted, but the wrapper is always "
"asynchronous, so the decorated callable must then be awaited or iterated "
"with ``async for``. If that change of calling convention is not intended, "
"use :class:`ContextDecorator` instead."
msgstr ""
msgid "Example of ``AsyncContextDecorator``::"
msgstr ""
msgid ""
"from asyncio import run\n"
"from contextlib import AsyncContextDecorator\n"
"\n"
"class mycontext(AsyncContextDecorator):\n"
" async def __aenter__(self):\n"
" print('Starting')\n"
" return self\n"
"\n"
" async def __aexit__(self, *exc):\n"
" print('Finishing')\n"
" return False"
msgstr ""
msgid ""
">>> @mycontext()\n"
"... async def function():\n"
"... print('The bit in the middle')\n"
"...\n"
">>> run(function())\n"
"Starting\n"
"The bit in the middle\n"
"Finishing\n"
"\n"
">>> async def function():\n"
"... async with mycontext():\n"
"... print('The bit in the middle')\n"
"...\n"
">>> run(function())\n"
"Starting\n"
"The bit in the middle\n"
"Finishing"
msgstr ""
msgid ""
"Decorating an asynchronous generator function now keeps the context manager "
"open across iteration. Previously the context manager exited as soon as the "
"generator object was created. Synchronous functions and synchronous "
"generator functions are also now accepted, with an asynchronous wrapper "
"returned."
msgstr ""
msgid ""
"A context manager that is designed to make it easy to programmatically "
"combine other context managers and cleanup functions, especially those that "
"are optional or otherwise driven by input data."
msgstr ""
msgid ""
"For example, a set of files may easily be handled in a single with statement "
"as follows::"
msgstr ""
msgid ""
"with ExitStack() as stack:\n"
" files = [stack.enter_context(open(fname)) for fname in filenames]\n"
" # All opened files will automatically be closed at the end of\n"
" # the with statement, even if attempts to open files later\n"
" # in the list raise an exception"
msgstr ""
msgid ""
"The :meth:`~object.__enter__` method returns the :class:`ExitStack` "
"instance, and performs no additional operations."
msgstr ""
msgid ""
"Each instance maintains a stack of registered callbacks that are called in "
"reverse order when the instance is closed (either explicitly or implicitly "
"at the end of a :keyword:`with` statement). Note that callbacks are *not* "
"invoked implicitly when the context stack instance is garbage collected."
msgstr ""
msgid ""
"This stack model is used so that context managers that acquire their "
"resources in their ``__init__`` method (such as file objects) can be handled "
"correctly."
msgstr ""
msgid ""
"Since registered callbacks are invoked in the reverse order of registration, "
"this ends up behaving as if multiple nested :keyword:`with` statements had "
"been used with the registered set of callbacks. This even extends to "
"exception handling - if an inner callback suppresses or replaces an "
"exception, then outer callbacks will be passed arguments based on that "
"updated state."
msgstr ""
msgid ""
"This is a relatively low level API that takes care of the details of "
"correctly unwinding the stack of exit callbacks. It provides a suitable "
"foundation for higher level context managers that manipulate the exit stack "
"in application specific ways."
msgstr ""
msgid ""
"Enters a new context manager and adds its :meth:`~object.__exit__` method to "
"the callback stack. The return value is the result of the context manager's "
"own :meth:`~object.__enter__` method."
msgstr ""
msgid ""
"These context managers may suppress exceptions just as they normally would "
"if used directly as part of a :keyword:`with` statement."
msgstr ""
msgid ""
"Raises :exc:`TypeError` instead of :exc:`AttributeError` if *cm* is not a "
"context manager."
msgstr ""
msgid ""
"Added support for arbitrary descriptors :meth:`!__enter__` and :meth:`!"
"__exit__`."
msgstr ""
msgid ""
"Adds a context manager's :meth:`~object.__exit__` method to the callback "
"stack."
msgstr ""
msgid ""
"As ``__enter__`` is *not* invoked, this method can be used to cover part of "
"an :meth:`~object.__enter__` implementation with a context manager's own :"
"meth:`~object.__exit__` method."
msgstr ""
msgid ""
"If passed an object that is not a context manager, this method assumes it is "
"a callback with the same signature as a context manager's :meth:`~object."
"__exit__` method and adds it directly to the callback stack."
msgstr ""
msgid ""
"By returning true values, these callbacks can suppress exceptions the same "
"way context manager :meth:`~object.__exit__` methods can."
msgstr ""
msgid ""
"The passed in object is returned from the function, allowing this method to "
"be used as a function decorator."
msgstr ""
msgid "Added support for arbitrary descriptors :meth:`!__exit__`."
msgstr ""
msgid ""
"Accepts an arbitrary callback function and arguments and adds it to the "
"callback stack."
msgstr ""
msgid ""
"Unlike the other methods, callbacks added this way cannot suppress "
"exceptions (as they are never passed the exception details)."
msgstr ""
msgid ""
"The passed in callback is returned from the function, allowing this method "
"to be used as a function decorator."
msgstr ""
msgid ""
"Transfers the callback stack to a fresh :class:`ExitStack` instance and "
"returns it. No callbacks are invoked by this operation - instead, they will "
"now be invoked when the new stack is closed (either explicitly or implicitly "
"at the end of a :keyword:`with` statement)."
msgstr ""
msgid ""
"For example, a group of files can be opened as an \"all or nothing\" "
"operation as follows::"
msgstr ""
msgid ""
"with ExitStack() as stack:\n"
" files = [stack.enter_context(open(fname)) for fname in filenames]\n"
" # Hold onto the close method, but don't call it yet.\n"
" close_files = stack.pop_all().close\n"
" # If opening any file fails, all previously opened files will be\n"
" # closed automatically. If all files are opened successfully,\n"
" # they will remain open even after the with statement ends.\n"
" # close_files() can then be invoked explicitly to close them all."
msgstr ""
msgid ""
"Immediately unwinds the callback stack, invoking callbacks in the reverse "
"order of registration. For any context managers and exit callbacks "
"registered, the arguments passed in will indicate that no exception occurred."
msgstr ""
msgid ""
"An :ref:`asynchronous context manager <async-context-managers>`, similar to :"
"class:`ExitStack`, that supports combining both synchronous and asynchronous "
"context managers, as well as having coroutines for cleanup logic."
msgstr ""
msgid ""
"The :meth:`~ExitStack.close` method is not implemented; :meth:`aclose` must "
"be used instead."
msgstr ""
msgid ""
"Similar to :meth:`ExitStack.enter_context` but expects an asynchronous "
"context manager."
msgstr ""
msgid ""
"Raises :exc:`TypeError` instead of :exc:`AttributeError` if *cm* is not an "
"asynchronous context manager."
msgstr ""
msgid ""
"Added support for arbitrary descriptors :meth:`!__aenter__` and :meth:`!"
"__aexit__`."
msgstr ""
msgid ""
"Similar to :meth:`ExitStack.push` but expects either an asynchronous context "
"manager or a coroutine function."
msgstr ""
msgid "Added support for arbitrary descriptors :meth:`!__aexit__`."
msgstr ""
msgid "Similar to :meth:`ExitStack.callback` but expects a coroutine function."
msgstr ""
msgid "Similar to :meth:`ExitStack.close` but properly handles awaitables."
msgstr ""
msgid "Continuing the example for :deco:`asynccontextmanager`::"
msgstr ""
msgid ""
"async with AsyncExitStack() as stack:\n"
" connections = [await stack.enter_async_context(get_connection())\n"
" for i in range(5)]\n"
" # All opened connections will automatically be released at the end of\n"
" # the async with statement, even if attempts to open a connection\n"
" # later in the list raise an exception."
msgstr ""
msgid "Examples and Recipes"
msgstr ""
msgid ""
"This section describes some examples and recipes for making effective use of "
"the tools provided by :mod:`!contextlib`."
msgstr ""
msgid "Supporting a variable number of context managers"
msgstr ""
msgid ""
"The primary use case for :class:`ExitStack` is the one given in the class "
"documentation: supporting a variable number of context managers and other "
"cleanup operations in a single :keyword:`with` statement. The variability "
"may come from the number of context managers needed being driven by user "
"input (such as opening a user specified collection of files), or from some "
"of the context managers being optional::"
msgstr ""
msgid ""
"with ExitStack() as stack:\n"
" for resource in resources:\n"
" stack.enter_context(resource)\n"
" if need_special_resource():\n"
" special = acquire_special_resource()\n"
" stack.callback(release_special_resource, special)\n"
" # Perform operations that use the acquired resources"
msgstr ""
msgid ""
"As shown, :class:`ExitStack` also makes it quite easy to use :keyword:`with` "
"statements to manage arbitrary resources that don't natively support the "
"context management protocol."
msgstr ""
msgid "Catching exceptions from ``__enter__`` methods"
msgstr ""
msgid ""
"It is occasionally desirable to catch exceptions from an :meth:`~object."
"__enter__` method implementation, *without* inadvertently catching "
"exceptions from the :keyword:`with` statement body or the context manager's :"
"meth:`~object.__exit__` method. By using :class:`ExitStack` the steps in the "
"context management protocol can be separated slightly in order to allow "
"this::"
msgstr ""
msgid ""
"stack = ExitStack()\n"
"try:\n"
" x = stack.enter_context(cm)\n"
"except Exception:\n"
" # handle __enter__ exception\n"
"else:\n"
" with stack:\n"
" # Handle normal case"
msgstr ""
msgid ""
"Actually needing to do this is likely to indicate that the underlying API "
"should be providing a direct resource management interface for use with :"
"keyword:`try`/:keyword:`except`/:keyword:`finally` statements, but not all "
"APIs are well designed in that regard. When a context manager is the only "
"resource management API provided, then :class:`ExitStack` can make it easier "
"to handle various situations that can't be handled directly in a :keyword:"
"`with` statement."
msgstr ""
msgid "Cleaning up in an ``__enter__`` implementation"
msgstr ""
msgid ""
"As noted in the documentation of :meth:`ExitStack.push`, this method can be "
"useful in cleaning up an already allocated resource if later steps in the :"
"meth:`~object.__enter__` implementation fail."
msgstr ""
msgid ""
"Here's an example of doing this for a context manager that accepts resource "
"acquisition and release functions, along with an optional validation "
"function, and maps them to the context management protocol::"
msgstr ""
msgid ""
"from contextlib import contextmanager, AbstractContextManager, ExitStack\n"
"\n"
"class ResourceManager(AbstractContextManager):\n"
"\n"
" def __init__(self, acquire_resource, release_resource, "
"check_resource_ok=None):\n"
" self.acquire_resource = acquire_resource\n"
" self.release_resource = release_resource\n"
" if check_resource_ok is None:\n"
" def check_resource_ok(resource):\n"
" return True\n"
" self.check_resource_ok = check_resource_ok\n"
"\n"
" @contextmanager\n"
" def _cleanup_on_error(self):\n"
" with ExitStack() as stack:\n"
" stack.push(self)\n"
" yield\n"
" # The validation check passed and didn't raise an exception\n"
" # Accordingly, we want to keep the resource, and pass it\n"
" # back to our caller\n"
" stack.pop_all()\n"
"\n"
" def __enter__(self):\n"
" resource = self.acquire_resource()\n"
" with self._cleanup_on_error():\n"
" if not self.check_resource_ok(resource):\n"
" msg = \"Failed validation for {!r}\"\n"
" raise RuntimeError(msg.format(resource))\n"
" return resource\n"
"\n"
" def __exit__(self, *exc_details):\n"
" # We don't need to duplicate any of our resource release logic\n"
" self.release_resource()"
msgstr ""
msgid "Replacing any use of ``try-finally`` and flag variables"
msgstr ""
msgid ""
"A pattern you will sometimes see is a ``try-finally`` statement with a flag "
"variable to indicate whether or not the body of the ``finally`` clause "
"should be executed. In its simplest form (that can't already be handled just "
"by using an ``except`` clause instead), it looks something like this::"
msgstr ""
msgid ""
"cleanup_needed = True\n"
"try:\n"
" result = perform_operation()\n"
" if result:\n"
" cleanup_needed = False\n"
"finally:\n"
" if cleanup_needed:\n"
" cleanup_resources()"
msgstr ""
msgid ""
"As with any ``try`` statement based code, this can cause problems for "
"development and review, because the setup code and the cleanup code can end "
"up being separated by arbitrarily long sections of code."
msgstr ""
msgid ""
":class:`ExitStack` makes it possible to instead register a callback for "
"execution at the end of a ``with`` statement, and then later decide to skip "
"executing that callback::"
msgstr ""
msgid ""
"from contextlib import ExitStack\n"
"\n"