How "expensive" are Exceptions?

[Michael 'Mickey' Lauer]

Hi, given the fact that excpetion handling can be very
expensive in languages like C++ - is python similar in
this aspect?

For instance, given somefunc() which sometimes (often)
returns a tuple and sometimes (rare) an integer - which version
would be to prefer?

Which version would be to prefer if the return types
are distributed evenly?

a)

try:
    a, b = somefunc()
except:
    return None
...
b)

selection = somefunc()
if len( selection ) != 2:
    return None
else:
    model, iter = selection
...

Yours,

Mickey.