On Wed, Apr 29, 2015 at 7:07 PM, Nick Coghlan <ncogh...@gmail.com> wrote:
> [...] > Yeah, I'm coming around to the idea. For the async pseudo-keyword, I > can see that the proposal only allows its use in cases that were > previously entirely illegal, but I'm not yet clear on how the PEP > proposes to avoid changing the meaning of the following code: > > x = await(this_is_a_function_call) > > Unless I'm misreading the proposed grammar in the PEP (which is > entirely possible), I believe PEP 492 would reinterpret that as: > > x = await this_is_not_a_function_call_any_more > Ah, but here's the other clever bit: it's only interpreted this way *inside* a function declared with 'async def'. Outside such functions, 'await' is not a keyword, so that grammar rule doesn't trigger. (Kind of similar to the way that the print_function __future__ disables the keyword-ness of 'print', except here it's toggled on or off depending on whether the nearest surrounding scope is 'async def' or not. The PEP could probably be clearer about this; it's all hidden in the Transition Plan section.) -- --Guido van Rossum (python.org/~guido)
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