[Python-Dev] PEP 362 Third Revision

[Steven D'Aprano]

Yury Selivanov wrote:
> On 2012-06-14, at 4:53 PM, Antoine Pitrou wrote:
>> On Wed, 13 Jun 2012 22:52:43 -0400
>> Yury Selivanov <yselivanov.ml at gmail.com> wrote:
>>
>>> * bind(\*args, \*\*kwargs) -> BoundArguments
>>>    Creates a mapping from positional and keyword arguments to
>>>    parameters.  Raises a ``BindError`` (subclass of ``TypeError``)
>>>    if the passed arguments do not match the signature.
>> Why a dedicated exception class? TypeError is good enough, and the
>> proliferation of exception classes is a nuisance.
> 
> 
> Agree.  Will fix this.


It's not broken. Within reason, more specific exceptions are better than less 
specific.

I have always considered it a wart that there was no supported way to 
programmatically distinguish between (say) len(42) and len("a", "b"). Both 
raise TypeError. Why is the second case a type error? It has nothing to do 
with the type of either len, "a" or "b".

The introduction of BindError will allow functions to raise a more specific, 
and less misleading, exception when they are called with the wrong number of 
arguments, or invalid keywords, etc.


-- 
Steven