[Tutor] Unable to catch exception

[James]

Kent,

I'm not importing BadStatusLine. I'm only importing mechanize, which
downloads a page repeatedly. From time to time a BadStatusLine
exception is raised. I'm unsure how to go about catching it.

Thoughts?

-j

On Sun, Aug 10, 2008 at 1:54 PM, Kent Johnson <kent37 at tds.net> wrote:
> On Sat, Aug 9, 2008 at 12:28 PM, James <jtp at nc.rr.com> wrote:
>> All,
>>
>> I'm having a rather strange problem that I'm hoping someone can shed
>> some light on. I'm trying to catch a BadStatusLine exception raised by
>> the httplib library.
>> The error only happens once every blue moon, but to avoid a crash I
>> setup a try/catch.
>>
>> try:
>>   <download page code here>
>> catch BadStatusLine:
>>   print "yuck!"
>>
>> However, somehow the thread that this code is in still raised a
>> BadStatusLine exception and the thread stopped cold.
>
> How did you import BadStatusLine?
>
> One strange gotcha about except statements is that the except clause
> is not evaluated until an exception is raised, so you can have an
> invalid name and you won't know it. For example this runs fine, even
> though foo is not defined:
> In [1]: try:
>   ...:     1
>   ...: except foo:
>   ...:     pass
>   ...:
> Out[1]: 1
>
> OTOH if an exception is raised it causes a NameError:
> In [2]: try:
>   ...:     1/0
>   ...: except foo:
>   ...:     pass
>   ...:
> ---------------------------------------------------------------------------
> <type 'exceptions.NameError'>             Traceback (most recent call last)
>
> /Users/kent/<ipython console> in <module>()
>
> <type 'exceptions.NameError'>: name 'foo' is not defined
>
> Kent
>