Find string between two substrings [duplicate]

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.

20 Answers

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

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).

start = 'asdf=5;' end = '123jasd' s = 'asdf=5;iwantthis123jasd' print s[s.find(start)+len(start):s.rfind(end)] 

gives

iwantthis 

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

String formatting adds some flexibility to what Nikolaus Gradwohl 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) 

If you don't want to import anything, try the string method .index():

text = 'I want to find a string between two substrings' left = 'find a ' right = 'between two' # Output: 'string' print(text[text.index(left)+len(left):text.index(right)]) 

Just converting the OP's own solution into an answer:

def find_between(s, start, end): return (s.split(start))[1].split(end)[0] 

source='your token _here0@df and maybe _here1@df or maybe _here2@df' start_sep='_' end_sep='@df' result=[] tmp=source.split(start_sep) for par in tmp: if end_sep in par: result.append(par.split(end_sep)[0]) print result 

must show: here0, here1, here2

the regex is better but it will require additional lib an you may want to go for python only

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) 

Here is a function I did to return a list with a string(s) inbetween string1 and string2 searched.

def GetListOfSubstrings(stringSubject,string1,string2): MyList = [] intstart=0 strlength=len(stringSubject) continueloop = 1 while(intstart < strlength and continueloop == 1): intindex1=stringSubject.find(string1,intstart) if(intindex1 != -1): #The substring was found, lets proceed intindex1 = intindex1+len(string1) intindex2 = stringSubject.find(string2,intindex1) if(intindex2 != -1): subsequence=stringSubject[intindex1:intindex2] MyList.append(subsequence) intstart=intindex2+len(string2) else: continueloop=0 else: continueloop=0 return MyList #Usage Example mystring="s123y123o123pp123y6" List = GetListOfSubstrings(mystring,"1","y68") for x in range(0, len(List)): print(List[x]) output: mystring="s123y123o123pp123y6" List = GetListOfSubstrings(mystring,"1","3") for x in range(0, len(List)): print(List[x]) output: 2 2 2 2 mystring="s123y123o123pp123y6" List = GetListOfSubstrings(mystring,"1","y") for x in range(0, len(List)): print(List[x]) output: 23 23o123pp123 

To extract STRING, try:

myString = '123STRINGabc' startString = '123' endString = 'abc' mySubString=myString[myString.find(startString)+len(startString):myString.find(endString)] 

You can simply use this code or copy the function below. All neatly in one line.

def substring(whole, sub1, sub2): return whole[whole.index(sub1) : whole.index(sub2)] 

If you run the function as follows.

print(substring("5+(5*2)+2", "(", "(")) 

You will pobably be left with the output:

(5*2 

rather than

5*2 

If you want to have the sub-strings on the end of the output the code must look like below.

return whole[whole.index(sub1) : whole.index(sub2) + 1] 

But if you don't want the substrings on the end the +1 must be on the first value.

return whole[whole.index(sub1) + 1 : whole.index(sub2)] 

These solutions assume the start string and final string are different. Here is a solution I use for an entire file when the initial and final indicators are the same, assuming the entire file is read using readlines():

def extractstring(line,flag='$'): if flag in line: # $ is the flag dex1=line.index(flag) subline=line[dex1+1:-1] #leave out flag (+1) to end of line dex2=subline.index(flag) string=subline[0:dex2].strip() #does not include last flag, strip whitespace return(string) 

Example:

lines=['asdf 1qr3 qtqay 45q at $A NEWT?$ asdfa afeasd', 'afafoaltat $I GOT BETTER!$ derpity derp derp'] for line in lines: string=extractstring(line,flag='$') print(string) 

Gives:

A NEWT? I GOT BETTER! 

This is essentially cji's answer - Jul 30 '10 at 5:58. I changed the try except structure for a little more clarity on what was causing the exception.

def find_between( inputStr, firstSubstr, lastSubstr ): ''' find between firstSubstr and lastSubstr in inputStr STARTING FROM THE LEFT above also has a func that does this FROM THE RIGHT ''' start, end = (-1,-1) try: start = inputStr.index( firstSubstr ) + len( firstSubstr ) except ValueError: print ' ValueError: ', print "firstSubstr=%s - "%( firstSubstr ), print sys.exc_info()[1] try: end = inputStr.index( lastSubstr, start ) except ValueError: print ' ValueError: ', print "lastSubstr=%s - "%( lastSubstr ), print sys.exc_info()[1] return inputStr[start:end] 

from timeit import timeit from re import search, DOTALL def partition_find(string, start, end): return string.partition(start)[2].rpartition(end)[0] def re_find(string, start, end): # applying re.escape to start and end would be safer return search(start + '(.*)' + end, string, DOTALL).group(1) def index_find(string, start, end): return string[string.find(start) + len(start):string.rfind(end)] # The wikitext of "Alan Turing law" article form English Wikipeida # string = """...""" start = '==Proposals==' end = '==Rival bills==' assert index_find(string, start, end) \ == partition_find(string, start, end) \ == re_find(string, start, end) print('index_find', timeit( 'index_find(string, start, end)', globals=globals(), number=100_000, )) print('partition_find', timeit( 'partition_find(string, start, end)', globals=globals(), number=100_000, )) print('re_find', timeit( 're_find(string, start, end)', globals=globals(), number=100_000, )) 

Result:

index_find 0.35047444528454114 partition_find 0.5327825636197754 re_find 7.552149639286381 

re_find was almost 20 times slower than index_find in this example.

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) 

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') """ 

Parsing text with delimiters from different email platforms posed a larger-sized version of this problem. They generally have a START and a STOP. Delimiter characters for wildcards kept choking regex. The problem with split is mentioned here & elsewhere - oops, delimiter character gone. It occurred to me to use replace() to give split() something else to consume. Chunk of code:

nuke = '~~~' start = '|*' stop = '*|' julien = (textIn.replace(start,nuke + start).replace(stop,stop + nuke).split(nuke)) keep = [chunk for chunk in julien if start in chunk and stop in chunk] logging.info('keep: %s',keep) 

Further from Nikolaus Gradwohl answer, I needed to get version number (i.e., 0.0.2) between('ui:' and '-') from below file content (filename: docker-compose.yml):

 version: '3.1' services: ui: image: repo-pkg.dev.io:21/website/ui:0.0.2-QA1 #network_mode: host ports: - 443:9999 ulimits: nofile:test 

and this is how it worked for me (python script):

import re, sys f = open('docker-compose.yml', 'r') lines = f.read() result = re.search('ui:(.*)-', lines) print result.group(1) Result: 0.0.2 

This seems much more straight forward to me:

import re s = 'asdf=5;iwantthis123jasd' x= re.search('iwantthis',s) print(s[x.start():x.end()])