New submission from Kaleb Barrett <[email protected]>:
Currently the __repr__ for TypeVar includes the variance information and the
type name (for example ~T, +T_co, -T_contra), but it does not contain bound or
constraint information. I'm not sure what value including variance but not
bound information in the __repr__ is, both are important for the use of
interfaces that use that variable.
I propose we add the bound and constraint information to the __repr__. The
__repr__ is arbitrary as popular type checking tools, such as mypy, and
documentation tools, such as Sphinx, do not use the standard __repr__. Nor is
the __repr__ eval()-able like many builtin types. And for documentation tools
that do use the standard __repr__, this improvement will be propagated to those
tools. (I originally requested this improvement in pdoc which uses the standard
__repr__; the maintainer agreed with this improvement.)
Bounds can be represented using an ASCII representation of the subset operator
"<=" and then the bound. Constraints can be represented using "<=" with a tuple
of the constraints. Perhaps spaces should be added around the "<=" operator? I
have no opinion.
Some examples of the proposed __repr__:
>>> TypeVar("T")
~T
>>> IntT = TypeVar("IntT", bound=int)
>>> IntT
~IntT<=int
>>> TypeVar("AnyStr", str, bytes)
~AnyStr<=(str, bytes)
>>> List[IntT]
List[~IntT<=int]
----------
messages: 415562
nosy: ktbarrett
priority: normal
severity: normal
status: open
title: Improve __repr__ of TypeVar
type: enhancement
versions: Python 3.11
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Python tracker <[email protected]>
<https://bugs.python.org/issue47068>
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