could ildg wrote:
> In re, the punctuation "^" can exclude a single character, but I want
> to exclude a whole word now. for example I have a string "hi, how are
> you. hello", I want to extract all the part before the world "hello",
> I can't use ".*[^hello]" because "^" only exclude single char "h" or
> "e" or "l" or "o". Will somebody tell me how to do it? Thanks.
import re
def demonstrate(regex, text):
pattern = re.compile(regex)
match = pattern.search(text)
print " ", text
if match:
print " Matched '%s'" % match.group(0)
print " Captured '%s'" % match.group(1)
else:
print " Did not match"
# Option 1: Match it all, but capture only the part before "hello." The
(.*?)
# matches as few characters as possible, so that this pattern would end
before
# the first hello in "hello hello".
pattern = r"(.*?)hello"
print "Option 1:", pattern
demonstrate( pattern, "hi, how are you. hello" )
# Option 2: Don't even match the "hello," but make sure it's there.
# The first of these calls will match, but the second will not. The
# (?=...) construct is using a feature called "forward look-ahead."
pattern = r"(.*)(?=hello)"
print "\nOption 2:", pattern
demonstrate( pattern, "hi, how are you. hello" )
demonstrate( pattern, "hi, how are you. ", )
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