i have a database
database=['3456734567','qqqqgtcgagagagctacgagaqqqqgtcgagagagctacgagaqqqqgtcgagagagctacgaga']
and I want to extract the repeated string as '34567' 'qqqqgtcgagagagctacgaga'
therefore I use the code as followings:
def string(s):
return re.search(r'(.+?)\1+', s).group(1)
print string(data[0])
print string(data[1])
however it only output '34567' and 'q'
please tell me how to edit and then get the result 'qqqqgtcgagagagctacgaga'
In this specific case, you can use a greedy operator instead of a non-greedy one:
r'(.+)\1+'
From documentation:
The
*,+, and?qualifiers are all greedy; they match as much text as possible. Sometimes this behaviour isn’t desired; if the RE<.*>is matched against<H1>title</H1>, it will match the entire string, and not just ''. Adding?after the qualifier makes it perform the match in non-greedy or minimal fashion; as few characters as possible will be matched. Using.*?in the previous expression will match only<H1>.
The below expression should give you the required result:
def string(s):
return re.search(r'(.+)\1+', s).group(1)
>>> print string(database[0])
34567
print string(database[1])
qqqqgtcgagagagctacgaga
Remove the '?' in your group, it makes the + qualifier eager, but you want a greedy one that matches as many repetitions as possible.
In [1]: re.match(r'(.+)\1+',
'qqqqgtcgagagagctacgagaqqqqgtcgagagagctacgagaqqqqgtcgagagagctacgaga').groups()
Out[1]: ('qqqqgtcgagagagctacgaga',)
Using .group() will only return the parentheses-wrapped part of the expression. You can use .start() and .end() to get the indices of the original string where the match happened:
def string(s):
match = re.search(r'(.+?)\1+', s)
return s[match.start() : match.end()] if match is not None else None
