undefined variable ?

[Josiah Carlson]

> Are exceptions cheap in Python then? Coming from Java, I know there's
> all sorts of overhead involved in creating and throwing an exception
> there...

They are not free, but they aren't that bad either...

>>> import time
>>> def te(n):
...     for i in xrange(n):
...         try:
...             j = 1
...         except:
...             pass
...
>>> def tf(n):
...     for i in xrange(n):
...         try:
...             raise #generally improper use
...         except:
...             pass
...
>>> def tf2(n):
...     for i in xrange(n):
...         try:
...             j = l
...         except:
...             pass
...
>>> def ne(n):
...     for i in xrange(n):
...         j = 1
...
>>> t = time.time();te(1000000);time.time()-t
0.92100000381469727
>>> t = time.time();tf(1000000);time.time()-t
7.7030000686645508
>>> t = time.time();tf(1000000);time.time()-t
27.0
>>> t = time.time();ne(1000000);time.time()-t
0.57899999618530273
>>>


The no-exception version runs in ~.58 seconds, with-exception handling 
(none raised) runs in ~.92 seconds, the first exception raiser runs in
~7.7 seconds, and the name error on assignment runs in ~27 seconds.


As long as you aren't relying on exception handling as a major part of
your algorithms, and are actually using them as /error handling/, I
wouldn't worry too much; the rest of us don't (we prefer properly
running scripts).

 - Josiah