[Python-Dev] Examples for PEP 572 (original) (raw)

David Mertz mertz at gnosis.cx
Wed Jul 4 10:20:35 EDT 2018

Hmmm... I admit I didn't expect quite this behavior. I'm don't actually understand why it's doing what it does.

def myfun(): ... print(globals().update({'foo', 43}), foo) ... myfun() Traceback (most recent call last): File "", line 1, in File "", line 2, in myfun TypeError: cannot convert dictionary update sequence element #0 to a sequence

That said, this is a silly game either way. And even though you CAN (sometimes) bind in an expression pre-572, that's one of those perverse corners that one shouldn't actually use.

On Wed, Jul 4, 2018 at 9:58 AM Chris Angelico <rosuav at gmail.com> wrote:

On Wed, Jul 4, 2018 at 11:52 PM, David Mertz <mertz at gnosis.cx> wrote: > On Wed, Jul 4, 2018 at 3:02 AM Chris Angelico <rosuav at gmail.com> wrote: >> >> "Assignment is a statement" -- that's exactly the point under discussion. >> "del is a statement" -- yes, granted >> "function and class declarations are statements" -- class, yes, but >> you have "def" and "lambda" as statement and expression equivalents. >> "import is a statement" -- but importlib.importmodule exists for a reason >> >> I'm going to assume that your term "mutating" there was simply a >> miswording, and that you're actually talking about name binding, >> which hitherto occurs only in statements. Yes, this is true. > > > Nope, not actually: > >>>> del foo >>>> print(globals().update({'foo':42}), foo) > None 42 >

Try it inside a function though. ChrisA

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