Gilles Ganault wrote:
> I stumbled upon something funny while downloading web pages and
> trying to extract one or more blocks from a page: Even though Python
> seems to return at least one block, it doesn't actually enter the for
> loop:
>
> ======
> re_block = re.compile('before (.+?) after',re.I|re.S|re.M)
>
> #Here, get web page and put it into "response"
>
> blocks = None
> blocks = re_block.finditer(response)
> if blocks == None:
> print "No block found"
> else:
> print "Before blocks"
> for block in blocks:
> #Never displayed!
> print "In blocks"
> ======
>
> Since "blocks" is no longer set to None after calling finditer()...
> but doesn't contain a single block... what does it contain then?
This is by design. When there are no matches re.finditer() returns an empty
iterator, not None.
Change your code to something like
has_matches = False
for match in re_block.finditer(response):
if not has_matches:
has_matches = True
print "before blocks"
print "in blocks"
if not has_matches:
print "no block found"
or
match = None
for match in re_block.finditer(response):
print "in blocks"
if match is None:
print "no block found"
Peter
--
http://mail.python.org/mailman/listinfo/python-list
