�&ǐk�@'bJ�h�ۊL'}T� :��'2�Z#$��n�a��� �>a��`��_3d�Qpt�/�P -��#5�,�M��� �pA:©�q�����NW��ډ�A���� �9nʺج���� �TSM��{J6?7��r�@�\����D��� �׶���s�f�TJj?"��D��`?��̒� b�#�%�C*v�$�{�$����5Ծ�F�s��y�e/8��h-�f�̰&(����Gj�L:U� 2�� ����v�_k����Y��gp,�k�WF�R������_C�R��N@���R�@�ߔ?A�w9���F("iNa-S���Q�o�3tDMLh*�#4k�T/iQ��Y*�G��m����)��8�hBm/�I�,g�ﯖ���Z��}�Cz�q@´��d.����L�ŕ�,��1�Z�܌�: ̪���F+J-'��c�tvJ8��]Q-��b��y �6;*J`r_�d ��'�G ~p��)'�C,�%F��E(��2�k�����lР�z�!�=t ��_�0��f7��� ;�p�|�U �%): try: yield finally: This makes this: with some_generator() as : equivalent to this: try: = finally: """ @wraps(func) def helper(*args, **kwds): return _GeneratorContextManager(func, args, kwds) return helper def asynccontextmanager(func): """@asynccontextmanager decorator. Typical usage: @asynccontextmanager async def some_async_generator(): try: yield finally: This makes this: async with some_async_generator() as : equivalent to this: try: = finally: """ @wraps(func) def helper(*args, **kwds): return _AsyncGeneratorContextManager(func, args, kwds) return helper class closing(AbstractContextManager): """Context to automatically close something at the end of a block. Code like this: with closing(.open()) as f: is equivalent to this: f = .open() try: finally: f.close() """ def __init__(self, thing): self.thing = thing def __enter__(self): return self.thing def __exit__(self, *exc_info): self.thing.close() class _RedirectStream(AbstractContextManager): _stream = None def __init__(self, new_target): self._new_target = new_target # We use a list of old targets to make this CM re-entrant self._old_targets = [] def __enter__(self): self._old_targets.append(getattr(sys, self._stream)) setattr(sys, self._stream, self._new_target) return self._new_target def __exit__(self, exctype, excinst, exctb): setattr(sys, self._stream, self._old_targets.pop()) class redirect_stdout(_RedirectStream): """Context manager for temporarily redirecting stdout to another file. # How to send help() to stderr with redirect_stdout(sys.stderr): help(dir) # How to write help() to a file with open('help.txt', 'w') as f: with redirect_stdout(f): help(pow) """ _stream = "stdout" class redirect_stderr(_RedirectStream): """Context manager for temporarily redirecting stderr to another file.""" _stream = "stderr" class suppress(AbstractContextManager): """Context manager to suppress specified exceptions After the exception is suppressed, execution proceeds with the next statement following the with statement. with suppress(FileNotFoundError): os.remove(somefile) # Execution still resumes here if the file was already removed """ def __init__(self, *exceptions): self._exceptions = exceptions def __enter__(self): pass def __exit__(self, exctype, excinst, exctb): # Unlike isinstance and issubclass, CPython exception handling # currently only looks at the concrete type hierarchy (ignoring # the instance and subclass checking hooks). While Guido considers # that a bug rather than a feature, it's a fairly hard one to fix # due to various internal implementation details. suppress provides # the simpler issubclass based semantics, rather than trying to # exactly reproduce the limitations of the CPython interpreter. # # See http://bugs.python.org/issue12029 for more details return exctype is not None and issubclass(exctype, self._exceptions) class _BaseExitStack: """A base class for ExitStack and AsyncExitStack.""" @staticmethod def _create_exit_wrapper(cm, cm_exit): return MethodType(cm_exit, cm) @staticmethod def _create_cb_wrapper(callback, /, *args, **kwds): def _exit_wrapper(exc_type, exc, tb): callback(*args, **kwds) return _exit_wrapper def __init__(self): self._exit_callbacks = deque() def pop_all(self): """Preserve the context stack by transferring it to a new instance.""" new_stack = type(self)() new_stack._exit_callbacks = self._exit_callbacks self._exit_callbacks = deque() return new_stack def push(self, exit): """Registers a callback with the standard __exit__ method signature. Can suppress exceptions the same way __exit__ method can. Also accepts any object with an __exit__ method (registering a call to the method instead of the object itself). """ # We use an unbound method rather than a bound method to follow # the standard lookup behaviour for special methods. _cb_type = type(exit) try: exit_method = _cb_type.__exit__ except AttributeError: # Not a context manager, so assume it's a callable. self._push_exit_callback(exit) else: self._push_cm_exit(exit, exit_method) return exit # Allow use as a decorator. def enter_context(self, cm): """Enters the supplied context manager. If successful, also pushes its __exit__ method as a callback and returns the result of the __enter__ method. """ # We look up the special methods on the type to match the with # statement. _cm_type = type(cm) _exit = _cm_type.__exit__ result = _cm_type.__enter__(cm) self._push_cm_exit(cm, _exit) return result def callback(*args, **kwds): """Registers an arbitrary callback and arguments. Cannot suppress exceptions. """ if len(args) >= 2: self, callback, *args = args elif not args: raise TypeError("descriptor 'callback' of '_BaseExitStack' object " "needs an argument") elif 'callback' in kwds: callback = kwds.pop('callback') self, *args = args import warnings warnings.warn("Passing 'callback' as keyword argument is deprecated", DeprecationWarning, stacklevel=2) else: raise TypeError('callback expected at least 1 positional argument, ' 'got %d' % (len(args)-1)) _exit_wrapper = self._create_cb_wrapper(callback, *args, **kwds) # We changed the signature, so using @wraps is not appropriate, but # setting __wrapped__ may still help with introspection. _exit_wrapper.__wrapped__ = callback self._push_exit_callback(_exit_wrapper) return callback # Allow use as a decorator callback.__text_signature__ = '($self, callback, /, *args, **kwds)' def _push_cm_exit(self, cm, cm_exit): """Helper to correctly register callbacks to __exit__ methods.""" _exit_wrapper = self._create_exit_wrapper(cm, cm_exit) self._push_exit_callback(_exit_wrapper, True) def _push_exit_callback(self, callback, is_sync=True): self._exit_callbacks.append((is_sync, callback)) # Inspired by discussions on http://bugs.python.org/issue13585 class ExitStack(_BaseExitStack, AbstractContextManager): """Context manager for dynamic management of a stack of exit callbacks. For example: with ExitStack() as stack: files = [stack.enter_context(open(fname)) for fname in filenames] # All opened files will automatically be closed at the end of # the with statement, even if attempts to open files later # in the list raise an exception. """ def __enter__(self): return self def __exit__(self, *exc_details): received_exc = exc_details[0] is not None # We manipulate the exception state so it behaves as though # we were actually nesting multiple with statements frame_exc = sys.exc_info()[1] def _fix_exception_context(new_exc, old_exc): # Context may not be correct, so find the end of the chain while 1: exc_context = new_exc.__context__ if exc_context is old_exc: # Context is already set correctly (see issue 20317) return if exc_context is None or exc_context is frame_exc: break new_exc = exc_context # Change the end of the chain to point to the exception # we expect it to reference new_exc.__context__ = old_exc # Callbacks are invoked in LIFO order to match the behaviour of # nested context managers suppressed_exc = False pending_raise = False while self._exit_callbacks: is_sync, cb = self._exit_callbacks.pop() assert is_sync try: if cb(*exc_details): suppressed_exc = True pending_raise = False exc_details = (None, None, None) except: new_exc_details = sys.exc_info() # simulate the stack of exceptions by setting the context _fix_exception_context(new_exc_details[1], exc_details[1]) pending_raise = True exc_details = new_exc_details if pending_raise: try: # bare "raise exc_details[1]" replaces our carefully # set-up context fixed_ctx = exc_details[1].__context__ raise exc_details[1] except BaseException: exc_details[1].__context__ = fixed_ctx raise return received_exc and suppressed_exc def close(self): """Immediately unwind the context stack.""" self.__exit__(None, None, None) # Inspired by discussions on https://bugs.python.org/issue29302 class AsyncExitStack(_BaseExitStack, AbstractAsyncContextManager): """Async context manager for dynamic management of a stack of exit callbacks. For example: async with AsyncExitStack() as stack: connections = [await stack.enter_async_context(get_connection()) for i in range(5)] # All opened connections will automatically be released at the # end of the async with statement, even if attempts to open a # connection later in the list raise an exception. """ @staticmethod def _create_async_exit_wrapper(cm, cm_exit): return MethodType(cm_exit, cm) @staticmethod def _create_async_cb_wrapper(callback, /, *args, **kwds): async def _exit_wrapper(exc_type, exc, tb): await callback(*args, **kwds) return _exit_wrapper async def enter_async_context(self, cm): """Enters the supplied async context manager. If successful, also pushes its __aexit__ method as a callback and returns the result of the __aenter__ method. """ _cm_type = type(cm) _exit = _cm_type.__aexit__ result = await _cm_type.__aenter__(cm) self._push_async_cm_exit(cm, _exit) return result def push_async_exit(self, exit): """Registers a coroutine function with the standard __aexit__ method signature. Can suppress exceptions the same way __aexit__ method can. Also accepts any object with an __aexit__ method (registering a call to the method instead of the object itself). """ _cb_type = type(exit) try: exit_method = _cb_type.__aexit__ except AttributeError: # Not an async context manager, so assume it's a coroutine function self._push_exit_callback(exit, False) else: self._push_async_cm_exit(exit, exit_method) return exit # Allow use as a decorator def push_async_callback(*args, **kwds): """Registers an arbitrary coroutine function and arguments. Cannot suppress exceptions. """ if len(args) >= 2: self, callback, *args = args elif not args: raise TypeError("descriptor 'push_async_callback' of " "'AsyncExitStack' object needs an argument") elif 'callback' in kwds: callback = kwds.pop('callback') self, *args = args import warnings warnings.warn("Passing 'callback' as keyword argument is deprecated", DeprecationWarning, stacklevel=2) else: raise TypeError('push_async_callback expected at least 1 ' 'positional argument, got %d' % (len(args)-1)) _exit_wrapper = self._create_async_cb_wrapper(callback, *args, **kwds) # We changed the signature, so using @wraps is not appropriate, but # setting __wrapped__ may still help with introspection. _exit_wrapper.__wrapped__ = callback self._push_exit_callback(_exit_wrapper, False) return callback # Allow use as a decorator push_async_callback.__text_signature__ = '($self, callback, /, *args, **kwds)' async def aclose(self): """Immediately unwind the context stack.""" await self.__aexit__(None, None, None) def _push_async_cm_exit(self, cm, cm_exit): """Helper to correctly register coroutine function to __aexit__ method.""" _exit_wrapper = self._create_async_exit_wrapper(cm, cm_exit) self._push_exit_callback(_exit_wrapper, False) async def __aenter__(self): return self async def __aexit__(self, *exc_details): received_exc = exc_details[0] is not None # We manipulate the exception state so it behaves as though # we were actually nesting multiple with statements frame_exc = sys.exc_info()[1] def _fix_exception_context(new_exc, old_exc): # Context may not be correct, so find the end of the chain while 1: exc_context = new_exc.__context__ if exc_context is old_exc: # Context is already set correctly (see issue 20317) return if exc_context is None or exc_context is frame_exc: break new_exc = exc_context # Change the end of the chain to point to the exception # we expect it to reference new_exc.__context__ = old_exc # Callbacks are invoked in LIFO order to match the behaviour of # nested context managers suppressed_exc = False pending_raise = False while self._exit_callbacks: is_sync, cb = self._exit_callbacks.pop() try: if is_sync: cb_suppress = cb(*exc_details) else: cb_suppress = await cb(*exc_details) if cb_suppress: suppressed_exc = True pending_raise = False exc_details = (None, None, None) except: new_exc_details = sys.exc_info() # simulate the stack of exceptions by setting the context _fix_exception_context(new_exc_details[1], exc_details[1]) pending_raise = True exc_details = new_exc_details if pending_raise: try: # bare "raise exc_details[1]" replaces our carefully # set-up context fixed_ctx = exc_details[1].__context__ raise exc_details[1] except BaseException: exc_details[1].__context__ = fixed_ctx raise return received_exc and suppressed_exc class nullcontext(AbstractContextManager): """Context manager that does no additional processing. Used as a stand-in for a normal context manager, when a particular block of code is only sometimes used with a normal context manager: cm = optional_cm if condition else nullcontext() with cm: # Perform operation, using optional_cm if condition is True """ def __init__(self, enter_result=None): self.enter_result = enter_result def __enter__(self): return self.enter_result def __exit__(self, *excinfo): pass