Paul Boddie p...@boddie.org.uk added the comment:
Actually, in the issue reported, the initial problem occurs in the evaluation
of an object in a boolean context (and the subsequent problem occurs with an
explicit len invocation):
http://www.selenic.com/pipermail/mercurial/2010-February/030066.html
Presumably (from memory and a brief look at the reference), when if data: is
evaluated, Python attempts to invoke an instance's __nonzero__ method or its
__len__ method. Since the mercurial.httprepo.httpsendfile class only provides a
__len__ method, the __len__ method's return value is used to determine truth.
The following demonstrates this particular issue:
class C:
... def __len__(self):
... return 2**35
...
c = C()
if c: pass
...
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: __nonzero__ should return an int
class C(object):
... def __len__(self):
... return 2**35
...
c = C()
if c: pass
...
Traceback (most recent call last):
File stdin, line 1, in module
OverflowError: long int too large to convert to int
Here, I could actually argue that the message mentioning __nonzero__ is
obscure: there isn't such a method defined, and __len__ is the misbehaving
method. Still, in the context of boolean evaluation, the OverflowError is less
helpful than it could be.
--
title: Inconsistent error types/messages for __len__ between old and new-style
classes - Inconsistent error types/messages for __len__ (and __nonzero__)
between old and new-style classes
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Python tracker rep...@bugs.python.org
http://bugs.python.org/issue7942
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