contextmanager.__enter__() Enter the runtime context and return either this object or another object related to the runtime context. The value returned by this method is bound to the identifier in the as clause of with statements using this context manager. An example of a context manager that returns itself is a file object. File objects return themselves from __enter__() to allow open() to be used as the context expression in a with statement. An example of a context manager that returns a

contextlib.suppress(*exceptions) Return a context manager that suppresses any of the specified exceptions if they occur in the body of a with statement and then resumes execution with the first statement following the end of the with statement. 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. For example: from contextl

contextlib.redirect_stdout(new_target) Context manager for temporarily redirecting sys.stdout to another file or file-like object. This tool adds flexibility to existing functions or classes whose output is hardwired to stdout. For example, the output of help() normally is sent to sys.stdout. You can capture that output in a string by redirecting the output to an io.StringIO object: f = io.StringIO() with redirect_stdout(f): help(pow) s = f.getvalue() To send the output of help() to a f

contextlib.redirect_stderr(new_target) Similar to redirect_stdout() but redirecting sys.stderr to another file or file-like object. This context manager is reentrant. New in version 3.5.

push(exit) Adds a context manager’s __exit__() method to the callback stack. As __enter__ is not invoked, this method can be used to cover part of an __enter__() implementation with a context manager’s own __exit__() method. 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 __exit__() method and adds it directly to the callback stack. By returning true values, these callbacks can suppress exceptions the same

pop_all() Transfers the callback stack to a fresh 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 with statement). For example, a group of files can be opened as an “all or nothing” operation as follows: with ExitStack() as stack: files = [stack.enter_context(open(fname)) for fname in filenames] # Hold onto the close method, but don't call it

enter_context(cm) Enters a new context manager and adds its __exit__() method to the callback stack. The return value is the result of the context manager’s own __enter__() method. These context managers may suppress exceptions just as they normally would if used directly as part of a with statement.

close() 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.

callback(callback, *args, **kwds) Accepts an arbitrary callback function and arguments and adds it to the callback stack. Unlike the other methods, callbacks added this way cannot suppress exceptions (as they are never passed the exception details). The passed in callback is returned from the function, allowing this method to be used as a function decorator.

class contextlib.ExitStack 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. For example, a set of files may easily be handled in a single with statement as follows: 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 stateme