[openstack-dev] [Review] Use of exception for non-exceptional cases

Nachi Ueno nachi at ntti3.com
Wed Jul 10 18:01:45 UTC 2013

HI folks

I would like to ask the review criteria in the community.

Should we use exception for non-exceptional cases when we can use
 parameter checking?

Example1:  Default value for array index

   value = list[5]
except IndexError:
    value = 'default_value'

This can be also written as,

     list_a[3] if len(list_a) > 3 else 'default_value'

"ask for forgiveness, not permission" is one of way in python,
however, on the other hand, google python code style guide says,
Minimize the amount of code in a try/except block. The larger the body
of the try, the more likely that an exception will be raised by a line
of code that you didn't expect to raise an exception. In those cases,
the try/except block hides a real error.

Personally, I prefer not to use exception for such cases.


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