On Thu, Jan 23, 2020 at 8:15 PM Andrew Svetlov <andrew.svet...@gmail.com> wrote:
>
> On Thu, Jan 23, 2020 at 5:46 PM Michael Anckaert via Python-Dev
> <python-dev@python.org> wrote:
> >
> > Hello everyone
> >
> > I have a usecase where I'm comparing a UUID instance with string quite
> > often. A case where I have to convert the UUID instance to a string
> > using str(uuid_obj), leading to redundant code:
> >
> > if str(uuid_obj) == uuid:
> > # do stuff...
> >
> > In my experience I can't find a case where you wouldn't want the
> > implicit conversion to string before comparing a UUID with string. So
> > I would like to propose improving the __eq__ method of UUID to:
> >
> > def __eq__(self, other):
> > if isinstance(other, UUID):
> > return self.int == other.int
> > elif isinstance(other, str):
> > return str(self) == other
> > return NotImplemented
> >
> > Based on my testing and experience I don't think this is a breaking
> > change and would be a meaningful change to the way UUID works. Of course
> > please don't hesitate to change my view or point out any flaws in my
> > reasoning.
> >
> > If other people support this change I'd start the work of creating an
> > issue and PR to get this change implemented.
>
> -1
> Implicit type casting leads to hidden errors very often.
I also tend to be against this change, for the same general reason
that Andrew gave, but let me try to put that into more concrete terms.
In the specific case of UUIDs in the uuid module, equivalent UUIDs can
be constructed in various ways using the UUID constructor, including
using different string formats. For example, the following strings are
considered equivalent UUIDs:
"00010203-0405-0607-0809-0a0b0c0d0e0f"
"{00010203-0405-0607-0809-0a0b0c0d0e0f}"
"000102030405060708090a0b0c0d0e0f"
"urn:uuid:00010203-0405-0607-0809-0a0b0c0d0e0f"
For more examples, see the uuid module's tests:
https://github.com/python/cpython/blob/7142df5ea23b4ce0efb72746b4b3b65414e8dcb1/Lib/test/test_uuid.py#L29
Using string comparison for UUIDs would be significantly different
than what comparing uuid.UUID objects does. Therefore, making
UUID.__eq__() fall back to string comparison would be confusing, IMO
much more so than it would be helpful.
- Tal Einat
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