Home Original page

[Python-ideas] PEP 428: poll about the joining syntax

Georg Brandl g.brandl at gmx.net
Fri Oct 12 18:12:26 CEST 2012 
Am 12.10.2012 14:45, schrieb Blake Hyde:
> I'm a Python developer rather than a developer of Python, but I'd like to ask a
> question about this option (and implicitly vote against it, I suppose); if you
> specialize a method name, such as .pathjoin, aren't you implying that methods
> must be unambiguous even across types and classes?  This seems negative.  Even
> if .join is already used for strings, it also makes sense for this use case.

Of course different classes can have methods of the same name.

The issue here is that due to the similarity (and interchangeability) of path
objects and strings it is likely that people get them mixed up every now and
then, and if .join() works on both objects the failure mode (strange result
from str.join when you expected path.join) is horribly confusing.

It's the same argument against the "+" operator.  (Apart from the other downside
that it will act differently depending on *two* objects, i.e. both operands.)
In contrast, the "/" operator is not defined on strings, but on numbers, and
the both the confusion likelihood and failure mode of mixing numbers and
strings are much less severe.

It's really kind of the same reason why integer floor division was awkward
with "/", and has been changed to "//" in Python 3.

Georg
More information about the Python-ideas mailing list