Sequence-length - Missing the obvious ?

[Michael Hudson]

aahz at netcom.com (Aahz Maruch) writes:

> In article <3938090C.9FB5D057 at stud.ntnu.no>,
> Peter Schneider-Kamp  <peter at schneider-kamp.de> wrote:
> >mlauer at trollinger-fe.rz.uni-frankfurt.de wrote:
> >> 
> >> But why ? How does the for loop knows
> >> how much elements the sequence contains ?
> >> I did not program the __len__ function,
> >> so... how ?
> >
> >As far as I understand the for loop goes on until an IndexError is
> >raised. Then the error is cleared and the for loop ends.
> 
> Let's be technically precise here: an exception is raised and caught by
> the "for" handler; the for loop is then broken (precisely as if the
> break statement was executed).  Like any other caught exception, the
> exception is thrown away (not "error is cleared").

Not quite "precisely as if the break statement was executed", wrt else
blocks.  Ponder the output of these two statements:

for i in range(10):
	print i
else:
	print "else"

for i in range(10):
	if i > 4: break
	print i
else:
	print "else"

but otherwise, yes.

Cheers,
M.

-- 
  The ability to quote is a serviceable substitute for wit.
                                                -- W. Somerset Maugham