I have the following small module:

=-=-=-=-=-=-=-=-=-=-=-= 8< =-=-=-=-=-=-=-=-=-=-=-=-=

from typing import NamedTuple, TypeAlias, Union
from collections.abc import Sequence

PNT: TypeAlias = tuple[float, float]

class Pnt (NamedTuple):
x: float
y: float

def __add__(self, other: PNT) -> Pnt:
return Pnt(self[0] + other[0], self[1] + other[1])

=-=-=-=-=-=-=-=-=-=-=-= >8 =-=-=-=-=-=-=-=-=-=-=-=-=

But when I import this, I get the following diagnostic:

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/sisc/projecten/iudex/problem.py", line 10, in <module>
class Pnt (NamedTuple):
File "/home/sisc/projecten/iudex/problem.py", line 14, in Pnt
def __add__(self, other: PNT) -> Pnt:
^^^
NameError: name 'Pnt' is not defined. Did you mean: 'PNT'?


Can someone explain what I am doing wrong?

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On 23/10/2023 04.50, Antoon Pardon via Python-list wrote:

I have the following small module:

=-=-=-=-=-=-=-=-=-=-=-= 8< =-=-=-=-=-=-=-=-=-=-=-=-=

from typing import NamedTuple, TypeAlias, Union
from collections.abc import Sequence

PNT: TypeAlias = tuple[float, float]

class Pnt (NamedTuple):
    x: float
    y: float

    def __add__(self, other: PNT) -> Pnt:
        return Pnt(self[0] + other[0], self[1] + other[1])

=-=-=-=-=-=-=-=-=-=-=-= >8 =-=-=-=-=-=-=-=-=-=-=-=-=

But when I import this, I get the following diagnostic:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/sisc/projecten/iudex/problem.py", line 10, in <module>
    class Pnt (NamedTuple):
  File "/home/sisc/projecten/iudex/problem.py", line 14, in Pnt
    def __add__(self, other: PNT) -> Pnt:
                                     ^^^ NameError: name 'Pnt' is not defined. Did you mean: 'PNT'?

Can someone explain what I am doing wrong?

What happens when the advice is followed?

Not sure why declare type-alias and then don't use it, but if insist on
using class-name will be making a "forward-reference" (because class has
not yet been fully defined) - see https://mypy.readthedocs.io/en/stable/cheat_sheet_py3.html#forward-references

--
Regards,
=dn

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On 22Oct2023 17:50, Antoon Pardon <antoon.pardon@vub.be> wrote:

I have the following small module:
=-=-=-=-=-=-=-=-=-=-=-= 8< =-=-=-=-=-=-=-=-=-=-=-=-=
class Pnt (NamedTuple):
x: float
y: float

def __add__(self, other: PNT) -> Pnt:
return Pnt(self[0] + other[0], self[1] + other[1])

When this function is defined, the class "Pnt" has not yet been defined.
That happens afterwards.

You want a forward reference, eg:

def __add__(self, other: PNT) -> "Pnt":

A type checker will resolve this after the fact, when it encounters the
string in the type annotation.

This message:

NameError: name 'Pnt' is not defined. Did you mean: 'PNT'?

is unfortunate, because you have a very similar "PNT" name in scope. But
it isn't what you want.

Cheers,
Cameron Simpson <cs@cskk.id.au>

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