Wolfgang Rohdewald wrote:
On Monday 05 October 2009, MRAB wrote:
You're currently looking for one that's not followed by another;
the solution is to check first whether there are two:
>>> re.match(r'(?!.*?C1.*?C1)(.*?C1)','C1b1b1b1 b3b3b3b3
C1C2C3').groups()
Traceback (most recent call last):
File "<pyshell#3>", line 1, in <module>
re.match(r'(?!.*?C1.*?C1)(.*?C1)','C1b1b1b1 b3b3b3b3
C1C2C3').groups() AttributeError: 'NoneType' object has no
attribute 'groups'
that is a nice solution!
now to make it more similar to my real world case
where C1 is actually part of the string:
same regex but using a group for C1 does not work - why?
re.match(r'(?!.*?(C1).*?\1)(.*?\1)','C1b1b1b1 b3b3b3b3 C2C2C3').groups()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'groups'
re.match(r'(?!.*?(?P<tile>C1).*?(?P=tile))(.*?(?P=tile))','C1B1B1B1 b3b3b3b3
C2C2C3').groups()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'groups'
"(?!.*?(C1).*?\1)" will succeed only if ".*?(C1).*?\1" has failed, in
which case the group (group 1) will be undefined (no capture).
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