Find string between two substrings

Question

How do I find a string between two substrings ('123STRINGabc' -> 'STRING')?

My current method is like this:

>>> start = 'asdf=5;'
>>> end = '123jasd'
>>> s = 'asdf=5;iwantthis123jasd'
>>> print((s.split(start))[1].split(end)[0])
iwantthis

However, this seems very inefficient and un-pythonic. What is a better way to do something like this?

Forgot to mention: The string might not start and end with start and end. They may have more characters before and after.

Answer 1

s[len(start):-len(end)]

Answer 2

My method will be to do something like,

find index of start string in s => i
find index of end string in s => j

substring = substring(i+len(start) to j-1)

Answer 3

s = "123123STRINGabcabc"

def find_between( s, first, last ):
    try:
        start = s.index( first ) + len( first )
        end = s.index( last, start )
        return s[start:end]
    except ValueError:
        return ""

def find_between_r( s, first, last ):
    try:
        start = s.rindex( first ) + len( first )
        end = s.rindex( last, start )
        return s[start:end]
    except ValueError:
        return ""


print find_between( s, "123", "abc" )
print find_between_r( s, "123", "abc" )

gives:

123STRING
STRINGabc

I thought it should be noted - depending on what behavior you need, you can mix index and rindex calls or go with one of the above versions (it's equivalent of regex (.*) and (.*?) groups).

Answer 4

Here is one way to do it

_,_,rest = s.partition(start)
result,_,_ = rest.partition(end)
print result

Another way using regexp

import re
print re.findall(re.escape(start)+"(.*)"+re.escape(end),s)[0]

or

print re.search(re.escape(start)+"(.*)"+re.escape(end),s).group(1)

Answer 5

import re

s = 'asdf=5;iwantthis123jasd'
result = re.search('asdf=5;(.*)123jasd', s)
print result.group(1)

Answer 6

This I posted before as code snippet in Daniweb:

# picking up piece of string between separators
# function using partition, like partition, but drops the separators
def between(left,right,s):
    before,_,a = s.partition(left)
    a,_,after = a.partition(right)
    return before,a,after

s = "bla bla blaa <a>data</a> lsdjfasdjöf (important notice) 'Daniweb forum' tcha tcha tchaa"
print between('<a>','</a>',s)
print between('(',')',s)
print between("'","'",s)

""" Output:
('bla bla blaa ', 'data', " lsdjfasdj\xc3\xb6f (important notice) 'Daniweb forum' tcha tcha tchaa")
('bla bla blaa <a>data</a> lsdjfasdj\xc3\xb6f ', 'important notice', " 'Daniweb forum' tcha tcha tchaa")
('bla bla blaa <a>data</a> lsdjfasdj\xc3\xb6f (important notice) ', 'Daniweb forum', ' tcha tcha tchaa')
"""

Answer 7

String formatting adds some flexibility to what NG suggested. start and end can now be amended as desired.

import re

s = 'asdf=5;iwantthis123jasd'
start = 'asdf=5;'
end = '123jasd'

result = re.search('%s(.*)%s' % (start, end), s).group(1)
print(result)