Patches item #1194449, was opened at 2005-05-03 13:18
Message generated for change (Comment added) made by gbrandl
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Category: Library (Lib)
Group: Python 2.4
>Status: Closed
>Resolution: Accepted
Priority: 5
Private: No
Submitted By: Jay T Miller (jaytmiller)
Assigned to: Ka-Ping Yee (ping)
Summary: pydoc requires o.__nonzero__() == True
Initial Comment:
On Tue, 2005-05-03 at 07:44, Nadav Horesh wrote:
>>> import numarray as N
> >>> a = N.array((2.3, 4.3))
> >>> N.__version__
> '1.3.1'
> >>> help(a.stddev)
>
> Traceback (most recent call last):
> File "<pyshell#11>", line 1, in -toplevel-
> help(a.stddev)
> File "/usr/local/lib/python2.4/site.py", line 328,
in __call__
> return pydoc.help(*args, **kwds)
> File "/usr/local/lib/python2.4/pydoc.py", line
1647, in __call__
> self.help(request)
> File "/usr/local/lib/python2.4/pydoc.py", line
1691, in help
> else: doc(request, 'Help on %s:')
> File "/usr/local/lib/python2.4/pydoc.py", line
1475, in doc
> pager(title % desc + '\n\n' +
text.document(object, name))
> File "/usr/local/lib/python2.4/pydoc.py", line 297,
in document
> if inspect.isroutine(object): return
self.docroutine(*args)
> File "/usr/local/lib/python2.4/pydoc.py", line
1226, in docroutine
> if object.im_self:
> File
"/usr/local/lib/python2.4/site-packages/numarray/generic.py",
> line 537, in __nonzero__
> raise RuntimeError("An array doesn't make sense
as a truth value.
> Use any(a) or all(a).")
> RuntimeError: An array doesn't make sense as a truth
value. Use any(a)
> or all(a).
> >>> help(a.sum)
>
>
In my opinion, this is a limitation (bug is maybe too
strong) of pydoc, in that pydoc's docroutine method
requires that an object be evaluable as a truth value
and that the result be True. I think that's a common,
but wrong, idiom.
I believe it's widely recognized that array's don't
make much sense as truth values because it leads to
code like this:
>>> a = array(5); b = array(8)
>>> a & b
array(0)
>>> if a & b:
... print "foo!"
foo!
Numeric expressions like the above implicitly mean
any(a & b) and appear to work but really contain subtle
bugs.
Hence, in numarray and Numeric3 (now or eventually),
the exception:
>>> if a & b:
... print "foo!"
...
Traceback (most recent call last):
...
RuntimeError: An array doesn't make sense as a truth
value. Use any(a) or all(a).
I think the pydoc docroutine() code should be changed
to read:
if object.im_self is not None:
and that particular limitation will be removed. I
submitted a patch.
Regards,
Todd
----------------------------------------------------------------------
>Comment By: Georg Brandl (gbrandl)
Date: 2007-03-13 22:17
Message:
Logged In: YES
user_id=849994
Originator: NO
Thanks for the patch, fixed in rev. 54365, 54366 (2.5).
----------------------------------------------------------------------
Comment By: Jay T Miller (jaytmiller)
Date: 2005-05-03 13:26
Message:
Logged In: YES
user_id=320512
The attached patch fixed my immediate problem but is
untested against the Python test suites. I did not do a
careful analysis for other uses of the "if o:" idiom but
noted that there are many of which I'm fixing two. I only
have anonymous access to Python CVS and it is unusable.
----------------------------------------------------------------------
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