Conditional context manager
I'm just throwing this idea out there to get feedback. Sometimes, I want to conditionally enter a context manager. This simplest (afaik) way of doing that is: with ExitStack() as stack: if condition: cm = stack.enter_context(cm_function()) suite() I suggest a more compact notation: with cm_function() as cm if condition: suite() I'm not sure that this is possible within the grammar. (For some reason with with_expr contains '"as" expr' rather than '"as" NAME'? I realize this comes up somewhat rarely. I use context managers a lot, and it comes up maybe 1 in 5k lines of code. For some extensions of this notation, an else clause could bind a value to cm in the case that condition is false. Best, Neil
On 2016-10-01 19:07, Neil Girdhar wrote:
If you defined a null context manager, you could then write: with (cm_function() if condition else cm_null()) as cm: suite() Do you need 'cm' itself? Its type changes depending on the condition, so I don't see how it could be useful. If it's not needed, then that shortens a little to: with cm_function() if condition else cm_null(): suite()
On Sun, Oct 2, 2016 at 5:07 AM, Neil Girdhar <mistersheik@gmail.com> wrote:
The simplest way would be to make a conditional version of the context manager. @contextlib.contextmanager def maybe_cm(state): if state: with cm_function() as cm: yield cm else: yield None I believe that'll work. ChrisA
On 2016-10-01 19:07, Neil Girdhar wrote:
If you defined a null context manager, you could then write: with (cm_function() if condition else cm_null()) as cm: suite() Do you need 'cm' itself? Its type changes depending on the condition, so I don't see how it could be useful. If it's not needed, then that shortens a little to: with cm_function() if condition else cm_null(): suite()
On Sun, Oct 2, 2016 at 5:07 AM, Neil Girdhar <mistersheik@gmail.com> wrote:
The simplest way would be to make a conditional version of the context manager. @contextlib.contextmanager def maybe_cm(state): if state: with cm_function() as cm: yield cm else: yield None I believe that'll work. ChrisA
participants (3)
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Chris Angelico -
MRAB -
Neil Girdhar