On 27 November 2014 at 23:04, Akira Li <4kir4.1i@gmail.com> wrote:
Stefano Borini <stefano.borini@ferrara.linux.it> writes:
I have a situation where, no matter how the routine ends, I need to return the focus to a widget. It would be rather clever to do this with a context, but I would expect something like this to be a possible strategy
with contextlib.context(enter=None, exit=lambda *args: my_widget.setFocus()): do what I need to do
as far as I know, at the moment it's not possible. Am I right? I think it would be an easy and practical addition to the contextlib module to quickly register two routines for enter and exit.
with ExitStack() as stack: stack.callback(my_widget.setFocus) cm = stack.enter_context(run_your_enter_routine())
https://docs.python.org/3/library/contextlib.html#contextlib.ExitStack
Right, while the underlying try/except/finally construct is generally a better option for simple cases of inline ad hoc exception handling, ExitStack is useful when you really do want to reproduce the context management protocols "pass the exception details to a callback" behaviour. For example, the feature requested by the OP can be implemented as: @contextmanager def context(enter=None, exit=None): enter_result = enter() if enter is not None else None with ExitStack() as stack: if exit is not None: stack.push(exit) yield enter_result However, I'm hard pressed to think of a case where using such a construct would be clearer than writing out a suitable try/except/finally block. A lot of the value of context managers lies in our ability to give them *names*, such that it's immediately clear what they're doing (or which docs to look up to find out more). Cheers, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia