diff options
Diffstat (limited to 'Lib/contextlib.py')
| -rw-r--r-- | Lib/contextlib.py | 80 |
1 files changed, 39 insertions, 41 deletions
diff --git a/Lib/contextlib.py b/Lib/contextlib.py index a564943..fb89118 100644 --- a/Lib/contextlib.py +++ b/Lib/contextlib.py @@ -37,6 +37,16 @@ class _GeneratorContextManager(ContextDecorator): def __init__(self, func, *args, **kwds): self.gen = func(*args, **kwds) self.func, self.args, self.kwds = func, args, kwds + # Issue 19330: ensure context manager instances have good docstrings + doc = getattr(func, "__doc__", None) + if doc is None: + doc = type(self).__doc__ + self.__doc__ = doc + # Unfortunately, this still doesn't provide good help output when + # inspecting the created context manager instances, since pydoc + # currently bypasses the instance docstring and shows the docstring + # for the class instead. + # See http://bugs.python.org/issue19404 for more details. def _recreate_cm(self): # _GCM instances are one-shot context managers, so the @@ -117,9 +127,6 @@ def contextmanager(func): return helper -# Unfortunately, this was originally published as a class, so -# backwards compatibility prevents the use of the wrapper function -# approach used for the other classes class closing(object): """Context to automatically close something at the end of a block. @@ -144,8 +151,18 @@ class closing(object): def __exit__(self, *exc_info): self.thing.close() -class _RedirectStdout: - """Helper for redirect_stdout.""" +class redirect_stdout: + """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) + """ def __init__(self, new_target): self._new_target = new_target @@ -163,25 +180,19 @@ class _RedirectStdout: self._old_target = self._sentinel sys.stdout = restore_stdout -# Use a wrapper function since we don't care about supporting inheritance -# and a function gives much cleaner output in help() -def redirect_stdout(target): - """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) - """ - return _RedirectStdout(target) +class suppress: + """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 + """ -class _SuppressExceptions: - """Helper for suppress.""" def __init__(self, *exceptions): self._exceptions = exceptions @@ -189,30 +200,17 @@ class _SuppressExceptions: pass def __exit__(self, exctype, excinst, exctb): - # Unlike isinstance and issubclass, exception handling only - # looks at the concrete type heirarchy (ignoring the instance - # and subclass checking hooks). However, all exceptions are - # also required to be concrete subclasses of BaseException, so - # if there's a discrepancy in behaviour, we currently consider it - # the fault of the strange way the exception has been defined rather - # than the fact that issubclass can be customised while the - # exception checks can't. + # 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) -# Use a wrapper function since we don't care about supporting inheritance -# and a function gives much cleaner output in help() -def suppress(*exceptions): - """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 - """ - return _SuppressExceptions(*exceptions) # Inspired by discussions on http://bugs.python.org/issue13585 class ExitStack(object): |