[Python-Dev] Please reject or postpone PEP 526 (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Sun Sep 4 14:31:59 EDT 2016

On 5 September 2016 at 04:13, Ivan Levkivskyi <levkivskyi at gmail.com> wrote:

On 4 September 2016 at 19:59, Nick Coghlan <ncoghlan at gmail.com> wrote:

I suspect you'll have an easier time of it on that front if you include some examples of dynamically typed code that a well-behaved type-checker must report as correct Python code, such as:

x: Optional[List[Any]] # This is the type of "x" after the if statement, not during it if arg is not None: x = list(arg) if otherarg is not None: # A well-behaved typechecker should allow this due to # the more specific initialisation in this particular branch x.extend(otherarg) else: x = None There are very similar examples in PEP 484 (section on singletons in unions), we could just copy those or use this example, but I am sure Guido will not agree to word "must" (although "should" maybe possible :-)

"Should" would be fine by me :)

Cheers, Nick.

-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia

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