Éric Araujo mer...@netwok.org added the comment:
Here’s my try at making the spec more explicit about str subclasses.
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keywords: +patch
Added file: http://bugs.python.org/file22244/pep--no-subclasses.diff
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Python tracker
Phillip J. Eby p...@telecommunity.com added the comment:
That change to the spec is fine, though you might also want to add something
like, Like all other WSGI specification types, since *all* types specified in
WSGI are 'type()' not 'isinstance()'.
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Éric Araujo mer...@netwok.org added the comment:
FYI, #10977 has been opened to tackle the general subclasses problem.
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Python tracker rep...@bugs.python.org
http://bugs.python.org/issue10935
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Phillip J. Eby p...@telecommunity.com added the comment:
Implicit knowledge in your own head about what might or might not be a good
idea to program is not the same thing as a specification. type(x) is str is
a good specification in this context, while string subclasses, but only if
they're
Antoine Pitrou pit...@free.fr added the comment:
Implicit knowledge in your own head about what might or might not be a
good idea to program is not the same thing as a specification.
type(x) is str is a good specification in this context, while
string subclasses, but only if they're really
Phillip J. Eby p...@telecommunity.com added the comment:
1. WSGI is a *Python* spec, not a *CPython* spec, so CPython implementation
details have little bearing on how the spec should work.
Most non-CPython implementations have a native string type optimized for their
runtime or VM (i.e.
R. David Murray rdmur...@bitdance.com added the comment:
4. The explicit-vs-implicit is about the contract defined in the spec (making
explicit what, precisely, is required of both parties), not the type test.
Perhaps a clarification in the () spec that 'type str' means type(s) is
str
Denis S. Otkidach denis.otkid...@gmail.com added the comment:
Phillip, your argument about interfacing with code written in C doesn't work
for built-in immutable types like str. Any subclass of str must call
str.__new__ thus keeping proper internal state.
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Jean-Paul Calderone invalid@example.invalid added the comment:
Phillip, your argument about interfacing with code written in C doesn't work
for built-in immutable types like str.
Sure it does. Definitely-str is easier to handle in C than maybe-str-subclass.
It doesn't matter that
Antoine Pitrou pit...@free.fr added the comment:
Jean-Paul Calderone invalid@example.invalid added the comment:
Phillip, your argument about interfacing with code written in C
doesn't work for built-in immutable types like str.
Sure it does. Definitely-str is easier to handle in C than
Andrey Popp 8may...@gmail.com added the comment:
I've also sent message[1] to web-sig about this issue.
[1]: http://mail.python.org/pipermail/web-sig/2011-January/004986.html
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Python tracker rep...@bugs.python.org
Phillip J. Eby p...@telecommunity.com added the comment:
PyString_AsString() only works on subclasses if their internal representation
is the same as type str. So we can't say subclass of str without *also*
specifying that the subclass store its contents in exactly the same way as an
object
Antoine Pitrou pit...@free.fr added the comment:
PyString_AsString() only works on subclasses if their internal
representation is the same as type str. So we can't say subclass of
str without *also* specifying that the subclass store its contents in
exactly the same way as an object of type
Denis S. Otkidach denis.otkid...@gmail.com added the comment:
Current behavior is unpythonic: documentation explicitly mentions isinstance as
preferred way to check type (see http://docs.python.org/library/types.html ).
Also 2.7 is the last minor version with str as main string type. So I
Phillip J. Eby p...@telecommunity.com added the comment:
Doesn't matter how unpythonic it is: the spec calls for exact types and has
done so for six years already, so it's a bit late to do anything about it.
(And any version of Python that allowed string subclasses was in violation of
the
Antoine Pitrou pit...@free.fr added the comment:
OK. So he is saying that when the spec says an object of type str he
means 'type(x) is str' as opposed to 'isinstance(x, str)'. I would
naively have expected the latter, as other people clearly do as well.
+1 with RDM here.
Doesn't matter
Andrey Popp 8may...@gmail.com added the comment:
the spec says an object of type str he means 'type(x) is str' as opposed to
'isinstance(x, str)'
-1 Liskov substitution principle states, that every subtype S of type T can be
used whenever type T is used.
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nosy: +andreypopp
Phillip J. Eby p...@telecommunity.com added the comment:
One of the original reasons was to make it easier for server authors writing C
code to interface with WSGI. C APIs that operate on lists and dicts often do
not do what you would expect, when called on a subclass. Essentially, this
New submission from Tim Perevezentsev riffm2...@gmail.com:
This code:
assert type(val) is StringType,Header values must be strings
(from here
http://svn.python.org/view/python/tags/r271/Lib/wsgiref/handlers.py?revision=86833view=markup)
from start_response method, is not allowing to use
Éric Araujo mer...@netwok.org added the comment:
This is by design. PEP 333 and PEP contain more information about that.
You’ll need to convert your objects to str before passing them to
start_response. Sorry!
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nosy: +eric.araujo, pje
resolution: - invalid
stage: -
Tim Perevezentsev riffm2...@gmail.com added the comment:
str - immutable. So every str subclass object is normal string. I don't see any
design violation here.
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http://bugs.python.org/issue10935
R. David Murray rdmur...@bitdance.com added the comment:
Eric, could you point out the part of the specification that requires exactly a
string and makes a string subclass invalid? I did a quick scan and couldn't
find it, and unfortunately don't have the time to re-read the whole spec right
Éric Araujo mer...@netwok.org added the comment:
See http://bugs.python.org/issue5800#msg121958
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http://bugs.python.org/issue10935
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R. David Murray rdmur...@bitdance.com added the comment:
OK. So he is saying that when the spec says an object of type str he means
'type(x) is str' as opposed to 'isinstance(x, str)'. I would naively have
expected the latter, as other people clearly do as well. I didn't participate
in any
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