Re: [Zope-dev] BUG: ValueError while changing height of the templateedit window
Casey Duncan wrote: On Tuesday 10 December 2002 03:14 pm, Guido van Rossum wrote: Can we get the same patch without the generic except:, please? the last thing I want is a database corruption caused by resizing the Edit box... Why would this particular except clause cause database corruption? I think Leonard is refering to catching ConflictErrors. However I don't think int() touches the database ;^). I saw try: int() except: pattern in many places through all the Zope code. I think catching ValueError only does the job, but then we should replace it in all the places. :-) -- Dmitry Vasiliev (dima at hlabs.spb.ru) ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] BUG: ValueError while changing height of the templateedit window
Guido van Rossum wrote:
Can we get the same patch without the generic except:, please?
snipped part about whether there could be database corruption
int() happens to raise a bunch of different exceptions, and I think
an unqualified except: clause is okay here (though it needs a
comment).
I think this would be a useful note for the Zope3 style guide.
What exceptions can int() raise?
On converting a preexisting value to an int:
ValueError, OverflowError, TypeError, AttributeError
(Any others?)
On converting an instance that implements __int__:
Anything at all.
It can even return a non-int value.
On evaluating the expression inside the int() brackets:
Anything at all.
I would suggest that only the four exceptions I listed first are worth
catching. The other cases are programming errors.
Of those four exceptions, in this situation, I think you only need to
catch ValueError. The other cases are application logic errors that I
think it is counterproductive to catch. If you get one, there is a bug
in some code, or some template, that should be fixed.
Here's how I produced the errors listed in the first category:
int('xxx')
Traceback (most recent call last):
File stdin, line 1, in ?
ValueError: invalid literal for int(): xxx
import sys
int(sys.maxint+1)
Traceback (most recent call last):
File stdin, line 1, in ?
OverflowError: long int too large to convert to int
int(int)
Traceback (most recent call last):
File stdin, line 1, in ?
TypeError: int() argument must be a string or a number
int(AttributeError())
Traceback (most recent call last):
File stdin, line 1, in ?
AttributeError: AttributeError instance has no attribute '__int__'
--
Steve Alexander
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Re: [Zope-dev] BUG: ValueError while changing height of the templateedit window
Anything can raise MemoryError. Ok. But I don't think regular application code should catch these. On converting an 8bit string to an int: ValueError *only* Ok. On converting a Unicode string to an int: ValueError UnicodeError (or UnicodeEncodeError, which is a subclass of it) Can you provide an example of raising a unicode error like this: u = makeUnicodeString() # your choice of function int(u) My point is that once you have a valid unicode object, I don't see how calling int(valid_unicode_object) will raise a UnicodeError. If this is so, then the style should be: value = expression_to_compute_value try: i = int(value) except ValueError: # take corrective action rather than: try: i = int(expression_to_compute_value) except: # Note: calling 'int()' can raise just about anything # take corrective action -- Steve Alexander ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] BUG: ValueError while changing height of the templateedit window
I spoke too soon. UnicodeEncodeError is a subclass of ValueError. So catching ValueError from int(str_or_unicode) is the way to go. Who's writing that Zope 3 style guide again? Great. http://dev.zope.org/Wikis/DevSite/Projects/ComponentArchitecture/ZopePythonStyleGuide -- Steve Alexander ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] BUG: ValueError while changing height of the templateedit window
Casey Duncan wrote: Please submit a collector issue for this http://collector.zope.org/Zope so the patch doesn't get lost. I tried it first, but my zope member login hadn't work yet and I had a problem with file uploading. I'm new with the collector, was I doing some things wrong? -- Dmitry Vasiliev (dima at hlabs.spb.ru) ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
