How to find overlapping matches with a regexp?

Question

>>> match = re.findall(r\'\\w\\w\', \'hello\')
>>> print match
[\'he\', \'ll\']

Since \\w\\w means two characters, \'he\' and \'l

Answer 1

findall doesn't yield overlapping matches by default. This expression does however:

>>> re.findall(r'(?=(\w\w))', 'hello')
['he', 'el', 'll', 'lo']

Here (?=...) is a lookahead assertion:

(?=...) matches if ... matches next, but doesn’t consume any of the string. This is called a lookahead assertion. For example, Isaac (?=Asimov) will match 'Isaac ' only if it’s followed by 'Asimov'.