Exception as the primary error handling mechanism?

[Peng Yu]

On Thu, Dec 31, 2009 at 11:24 PM, Chris Rebert <clp2 at rebertia.com> wrote:
> On Thu, Dec 31, 2009 at 8:47 PM, Peng Yu <pengyu.ut at gmail.com> wrote:
>> I observe that python library primarily use exception for error
>> handling rather than use error code.
>>
>> In the article API Design Matters by Michi Henning
>>
>> Communications of the ACM
>> Vol. 52 No. 5, Pages 46-56
>> 10.1145/1506409.1506424
>> http://cacm.acm.org/magazines/2009/5/24646-api-design-matters/fulltext
>>
>> It says "Another popular design flaw—namely, throwing exceptions for
>> expected outcomes—also causes inefficiencies because catching and
>> handling exceptions is almost always slower than testing a return
>> value."
>>
>> My observation is contradicted to the above statement by Henning. If
>> my observation is wrong, please just ignore my question below.
>>
>> Otherwise, could some python expert explain to me why exception is
>> widely used for error handling in python? Is it because the efficiency
>> is not the primary goal of python?
>
> Correct; programmer efficiency is a more important goal for Python instead.
> Python is ~60-100x slower than C;[1] if someone is worried by the
> inefficiency caused by exceptions, then they're using completely the
> wrong language.

Could somebody let me know how the python calls and exceptions are
dispatched? Is there a reference for it?