Heisenberg strikes again!

[Duncan Booth]

"David C. Fox" <davidcfox at post.harvard.edu> wrote in 
news:nRM7b.311656$Oz4.100417 at rwcrnsc54:

>>     throwaway = matches[0]   # <--- Comment out this line
> 
> When comp is called with state == 0, matches is still referring to the 
> local list which is not empty (unless there were no matches to the 
> text), so this line does indeed do nothing.  However, when comp is 
> called with state != 0, this line refers to the global matches list, 
> which is empty, so it raises an IndexError, and the following line is 
> not reached.

Not quite true there. Whether or not state is 0, this line always tries to 
access the local variable 'matches'. If you assign to a variable anywhere 
in a function (and don't declare it global), then all accesses in the 
function are to the local variable, not the global.

Of course the effect is basically the same, the function throws an 
exception either way, its just a different exception.

-- 
Duncan Booth                                             duncan at rcp.co.uk
int month(char *p){return(124864/((p[0]+p[1]-p[2]&0x1f)+1)%12)["\5\x8\3"
"\6\7\xb\1\x9\xa\2\0\4"];} // Who said my code was obscure?