Bare Excepts

[Victor Subervi]

On Wed, Dec 30, 2009 at 9:04 AM, Jean-Michel Pichavant <
jeanmichel at sequans.com> wrote:

> Victor Subervi wrote:
>
>> Hi;
>> I'll trouble-shoot bare excepts as I work on new code. I'll trouble-shoot
>> the others that don't (seem to) cause problems later. Here's a new one:
>>
>>    for optionsStore, storeOptions in ourOptions().iteritems():
>>      if store == optionsStore:
>>        for option in storeOptions:
>>          try:
>>            fromForm = form.getfirst(option)
>>            try:
>>              fromForm, junk = string.split(fromForm, ':')
>>            except:
>>              pass # This is only an expedient to split options that have a
>> colon in them, such as the colors
>>            fromForm = string.replace(fromForm, '-', '')
>>            sql = 'select "%s" from %s%s t join %s p where p.ID=t.ID;' %
>> (fromForm, store, (option[0].upper() + option[1:]), store)
>> #            print sql
>>            cursor.execute(sql)
>>            try:
>>              optionsPrices += cursor.fetchone()[0]
>>            except TypeError:
>>              pass # There is no options price for this.
>>          except:
>>            raise
>>  If there are no values entered into table (in this case "productsSizes")
>> for the given product ID, then "optionsPrices" should not be added unto. Am
>> I doing this correctly? Or is there a better way than capturing ALL
>> TypeErrors?
>> TIA,
>> beno
>>
> Hello,
>
> Do not use the 'try except' clause when 'if then' can perfectly handle the
> case.
>
> i.e.
>
>           try:
>             fromForm, junk = string.split(fromForm, ':')
>           except:
>             pass # This is only an expedient to split options that have a
> colon in them, such as the colors
>
> would be better written
>
>
> # This is only an expedient to split options that have a colon in them,
> such as the colors
> if ':' in fromForm:
>   fromForm, junk = fromForm.split(':')
>
> or
>
> fromForm = fromForm.split(':')[0]
>
>
> Anyway, you should definitely use a coding rule checker, like pylint or
> pyckeck. It would sometimes point you into the correct direction. For
> instance, pylint will tell you that except: pass is often (not always) a
> clue for bad design/pattern and issue warnings for it.
>
> In a more general manner, use try blocks when the code can throw exceptions
> upon condition you do not control. When you know about the conditions, use
> the if statement.
>
> No:
>
> a = None
> try:
>   a.split()
> except AttributeError:
>   pass
>
>
> Yes:
>
> a = None
> if a:
>   a.split()
>
> Exception are required in the following example:
>
> try:
>   main()
> except KeyboardInterrupt:
>   print 'interrupted by user'
>
> Cheers,
>
> JM
>
> Thank you.
beno
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