How to get the formal args of a function object?

[norseman]

Scott David Daniels wrote:
> kj wrote:
>> Suppose that f is an object whose type is 'function'.
>>
>> Is there a way to find out f's list of formal arguments?
>>
>> The reason for this is that I'm trying to write a decorator and
>> I'd like the wrapper to be able to check the number of arguments
>> passed....but I'm missing something like the hypothetical attribute
>> FORMAL_ARGS above.
> 
> I can write a wrapper now:
> 
>     def tracer(function):
>         def internal(*args, **kwargs):
>             print('calling %s(%s)' % (function.__name__,
>                     ', '.join([repr(arg) for arg in args] +
>                               ['%s=%r' % ka for ka in sorted(kwargs)])))
>             result = function(*args, **kwargs)
>             print('=> %r' % result)
>         return internal
> 
> and call like so:
>     tracer(math.sin)(3.1415 / 6)
> 
>     calling sin(0.5235833333333334)
>     => 0.49998662654663256
> 
> What would your missing something be for tracer(math.sin)?
> 
> --Scott David Daniels
> Scott.Daniels at Acm.Org
=========================
Scott;
I'm lost with this.

If you use the same and add that it prints both the first_token/second 
and the first_token multiplied by second and pass it (pi, 6, 7)  what 
happens then?

ie - function mysin only expects pi and 6 and is to print both pi/6 and 
pi*6.  The 7 is an error, not supposed to be there.



Steve