[Python-Dev] Re: typing: how to use names in result-tuples?

Yes, maybe I can use that. With Python >= 3.6, also def f() -> typing.NamedTuple("__f", x=int, y=int): ... which is concise, but a slightly weird abuse. But there are other drawbacks:

...

...

typing.Tuple[int, int] typing.Tuple[int, int] typing.Tuple[int, int] is typing.Tuple[int, int] True

versus

...

...

typing.NamedTuple("__f", x=int, y=int) typing.NamedTuple("__f", x=int, y=int) is typing.NamedTuple("__f", x=int, y=int) False

I think the whole NameTuple implementation looks a bit half-hearted, so I was looking to find something that is closer to the perfect behavior of the other typing types. Maybe I should try to implement something that keeps proper identity like Tuple and avoids the useless function name? Like def f() -> typing.KwTuple(x=int, y=int): ... or def f() -> typing.KwTuple([("x", int), ("y", int)]): ... cheers -- Chris On 29.07.19 18:00, Guido van Rossum wrote:

Can't you use the proper inline form of NamedTuple?

def f() -> typing.NamedTuple("__f", [("x", int), ("y", int)]):     ...

seems to work.

On Mon, Jul 29, 2019 at 8:26 AM Christian Tismer mailto:tismer@stackless.com> wrote:

Hi friends,

I am meanwhile the PySide maintainer at The Qt Company, and we are trying to make the mapping from Qt functions to Python functions as comparable as possible.

One problem are primitive pointer variables: In Qt, it is natural to use "sometype *varname" to make a mutable variable. In Python, you have to turn such a thing into a result-tuple. Example:

    void QPrinter::getPageMargins(qreal *left, qreal *top, \         qreal *right, qreal *bottom, QPrinter::Unit unit) const

(meanwhile deprecated, but a good example)

is mapped to the Python signature

    def getPageMargins(self, \         unit: PySide2.QtPrintSupport.QPrinter.Unit) \         -> typing.Tuple[float, float, float, float]: ...

NOW my question: ----------------

I would like to retain the variable names in Python! The first idea is to use typing.NamedTuple, but I get the impression that this would be too much, because I would not only need to create an extra named tuple definition for every set of names, but also invent a name for that named tuple.

What I would like to have is something that looks like

    def getPageMargins(self, \         unit: PySide2.QtPrintSupport.QPrinter.Unit) \         -> typing.NamedTuple[left: float, top: float, \                              right:float, bottom:float]: ...

but that is obviously not a named tuple. Possible would be to derive a name from the function, so maybe a definition could be used like

class PageMargingResult(NamedTuple):     left: float     top: float     right: float     bottom: float

but then I would have some opaque PageMargingResult type. This would work, but as said, this is a bit too much, since I only wanted something like a tuple with names.

What do you suggest to do here? Something what I am missing?

Cheers -- Chris -- Christian Tismer             :^)   tismer@stackless.com mailto:tismer@stackless.com Software Consulting          :     http://www.stackless.com/ Karl-Liebknecht-Str. 121     :     https://github.com/PySide 14482 Potsdam                :     GPG key -> 0xFB7BEE0E phone +49 173 24 18 776  fax +49 (30) 700143-0023

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-- Christian Tismer :^) tismer@stackless.com Software Consulting : http://www.stackless.com/ Karl-Liebknecht-Str. 121 : https://github.com/PySide 14482 Potsdam : GPG key -> 0xFB7BEE0E phone +49 173 24 18 776 fax +49 (30) 700143-0023