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How to extract the substring between two markers?
(22 answers)
Closed 4 years ago.
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.
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)
Just converting the OP's own solution into an answer:
def find_between(s, start, end):
return (s.split(start))[1].split(end)[0]
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)])
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
http://stackoverflow.com/questions/3368969/find-string-between-two-substrings
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
# https://en.wikipedia.org/w/index.php?title=Alan_Turing_law&action=edit&oldid=763725886
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()])
Related
I am trying to iterate over some integer values and insert them into an string which has to be in a weird format to work. The exact output (including the outer quotes) I need if the value was 64015 would be:
"param={\"zip\":\"64015\"}"
I have tried f string formatting but couldn't get it to work. It has problem with the backslashes and when I escaped them the output was not exactly like above string
Hopefully, I made myself clear enough.
You would have to escape the backslash and the double quotes seperately like this:
string = '"param={\\\"zip\\\":\\\"' + str(64015) + '\\\"}"'
The result of this is:
"param={\"zip\":\"64015\"}"
You can use alternate ways to delimit the outer string ('...', '''...''', """...""") or use str.format() or old style %-formatting syntax to get there (see f-style workaround at the end):
s = s = 'param={"zip":"' + str(64015) + '"}'
print(s)
s = '''param={"zip":"''' + str(64015) +'''"}'''
print(s)
s = """param={"zip":"64015"}""" # not suited for variable replacement
print(s)
s = 'param={{"zip":"{0}"}}'.format(64015)
print(s)
s = 'param={"zip":"%s"}' % 64015
print(s)
Output:
param={"zip":"64015"}
param={"zip":"64015"}
param={"zip":"64015"}
param={"zip":"64015"}
If you need any "\" in there simply drop a \\ in:
s = '"param={\\"zip\\":\\"' + str(64015) + '\\"}"'
print(s)
s = '''"param={\\"zip\\":\\"''' + str(64015) +'''\\"}"'''
print(s)
s = '"param={{\\"zip\\":\\"{0}\\"}}"'.format(64015)
print(s)
s = '"param={\\"zip\\":\\"%s\\"}"' % 64015
print(s)
Output:
"param={\"zip\":\"64015\"}"
"param={\"zip\":\"64015\"}"
"param={\"zip\":\"64015\"}"
"param={\"zip\":\"64015\"}"
The f-string workaround variant would look like so:
a = '\\"'
num = 64015
s = f'"param={{{a}zip{a}:{a}{num}{a}}}"'
and if printed also yields :
"param={\"zip\":\"64015\"}"
More on the topic can be found here: 'Custom string formatting' on python.org
I played around a bit with f-strings and .format() but ultimately got this to work:
foo = 90210
bar = '"param={\\"zip\\":\\"%s\\"}"' % (foo)
print(bar)
giving:
"param={\"zip\":\"90210\"}"
Hopefully someone can give you an f-string alternative. I kept running into unallowed "\" in my f-string attempts.
Is it only this?
a = "param={\"zip\":\"64015\"}"
b = a.split('=')
c = eval(b[1])
print(c)
print(c['zip'])
Result:
{'zip': '64015'}
64015
Please note that evaluating (eval()) strings from unknown source may
be dangerous! It may run the code that you are not expecting.
I need to remove all the numbers from the string recursively and then return the reversed string.
def remove_numbers_and_reverse(string):
if string == "":
return string
elif string[-1].isdigit():
string.replace(string[-1], "")
return string[-1] + remove_numbers_and_reverse(string[:-1])
For example if the input is "bunny1234" then the output should be "ynnub". But i get "4321ynnub".
"bunny1234" -> "ynnub"
"3434string" -> "gnirts"
For Removing number try below approach:
1. using join and isdigit
ini_string = "Test123ing127you"
print("initial string : ", ini_string)
res = ''.join([i for i in ini_string if not i.isdigit()])
print("final string : ", res)
2. Using translate and digits
from string import digits
ini_string = "Test123ing127you"
remove_digits = str.maketrans('', '', digits)
res = ini_string.translate(remove_digits)
# printing result
print("final string : ", res)
3. Using filter and lambda
ini_string = "amol23bais"
res = "".join(filter(lambda x: not x.isdigit(), ini_string))
# printing result
print("final string : ", str(res))
The problem with your solution is the elifpart: You are not doing anything with your replaced string, replace is not working in-place. So instead you might try this:
def remove_numbers_and_reverse(string):
if string == "":
return string
elif string[-1].isdigit():
return remove_numbers_and_reverse(string[:-1])
else:
return string[-1] + remove_numbers_and_reverse(string[:-1])
print(remove_numbers_and_reverse("bunny1234"))
print(remove_numbers_and_reverse("3434string"))
Here I just ignore the last character if it is a digit.
For shorter and smarter solutions see #Amolb's answer.
Other people have answered it but might as well throw in my example too.
def remove_numbers_and_reverse(my_string):
if not my_string:
return my_string
else:
for letter in my_string:
if letter.isdigit():
continue
output = letter + output
return output
The output:
[user#machine test-dir]$ python3
Python 3.6.9 (default, Aug 15 2019, 16:59:35)
>>> import test
>>> test.remove_numbers_and_reverse("bunny1234")
'ynnub'
>>> test.remove_numbers_and_reverse("3434string")
'gnirts'
>>> test.remove_numbers_and_reverse("3434string123123morestring")
'gnirtseromgnirts'
>>> test.remove_numbers_and_reverse("")
''
>>>
so today I was working on a function that removes any quoted strings from a chunk of data, and replaces them with format areas instead ({0}, {1}, etc...).
I ran into a problem, because the output was becoming completely scrambled, as in a {1} was going in a seemingly random place.
I later found out that this was a problem because the replacement of slices in the list changed the list so that it's length was different, and so the previous re matches would not line up (it only worked for the first iteration).
the gathering of the strings worked perfectly, as expected, as this is most certainly not a problem with re.
I've read about mutable sequences, and a bunch of other things as well, but was not able to find anything on this.
what I think i need is something like str.replace but can take slices, instead of a substring.
here is my code:
import re
def rm_strings_from_data(data):
regex = re.compile(r'"(.*?)"')
s = regex.finditer(data)
list_data = list(data)
val = 0
strings = []
for i in s:
string = i.group()
start, end = i.span()
strings.append(string)
list_data[start:end] = '{%d}' % val
val += 1
print(strings, ''.join(list_data), sep='\n\n')
if __name__ == '__main__':
rm_strings_from_data('[hi="hello!" thing="a thing!" other="other thing"]')
i get:
['"hello!"', '"a thing!"', '"other thing"']
[hi={0} thing="a th{1}r="other thing{2}
I would like the output:
['"hello!"', '"a thing!"', '"other thing"']
[hi={0} thing={1} other={2}]
any help would be appreciated. thanks for your time :)
Why not match both key=value parts using regex capture groups like this: (\w+?)=(".*?")
Then it becomes very easy to assemble the lists as needed.
Sample Code:
import re
def rm_strings_from_data(data):
regex = re.compile(r'(\w+?)=(".*?")')
matches = regex.finditer(data)
strings = []
list_data = []
for matchNum, match in enumerate(matches):
matchNum = matchNum + 1
strings.append(match.group(2))
list_data.append((match.group(1) + '={' + str(matchNum) + '} '))
print(strings, '[' + ''.join(list_data) + ']', sep='\n\n')
if __name__ == '__main__':
rm_strings_from_data('[hi="hello!" thing="a thing!" other="other thing"]')
Good afternoon everyone,
I'm trying to sort out names which are already sorted in alphabetical order. I can't figure out why my program isn't working. Any tips or pointers would be nice. Thanks.
def main():
names = ['Ava Fiscer', 'Bob White', 'Chris Rich', 'Danielle Porter', 'Gordon Pike', 'Hannah Beauregard', 'Matt Hoyle', 'Ross Harrison', 'Sasha Ricci', 'Xavier Adams']
input('Please enter the name to be searched: ', )
binarySearch
main()
def binarySearch(names):
first = 0
last = len(names) - 1
position = -1
found = False
while not found and first <= last:
middle = (first + last) / 2
if names[middle] == value:
found = True
position = middle
elif arr[middle] > value:
last = middle -1
else:
first = middle + 1
return position
What does it mean that the program isn't working? Is it a syntax error or is the problem in the wrong results?
With the code you pasted, there are several indentation problems, but besides that, lines:
input('Please enter the name to be searched: ', )
binarySearch
are also syntactically incorrect, the comma is redundant and only the function name appearing just like that is plain wrong. If you are interested in the correctness of your algorithm, it seems alright, but the boundaries can always be tricky. My code below is working and syntactically correct, if you find it helpful. (names are numbers, but that is irrelevant in this case)
names = [1,2,4,5,6,8,9]
def bs(n):
start = 0
end = len(names)
while end - start > 0:
m = (start+end)/2
if names[m] == n:
return m
elif n < names[m]:
end = m
else:
start = m + 1
return -1
print (bs(1))
print (bs(6))
print (bs(9))
print (bs(3))
print (bs(10))
print (bs(-8))
Another thing I would like to point out is that this kind of binary search is already in the python standard library, the bisect module. However, if you are writing your own for practice or for any other reason that is just fine.
if you are using python 3.* then you are going to want to change
m = (start+end)/2
to
m = (start+end)//2
When you do /2 it outputs a float in 3.*
I've found many related questions, and a couple that have at least helped me get this far. My goal is to have a function that receives a string and an arbitrary number of integers. I want the function to return that string with spaces inserted at the points given in the arguments. I will use this function with many different strings that will have varying numbers of inserts and insert locations.
This is an example of what I'd like to produce:
Input a string like 'ATGCATGCATGCATGC' and indexes (e.g. 4, 7). The output should be 'ATGCA TGC ATGCATGC'.
This is the function that has given me the closest results so far:
def breakRNA(seqRNA, *breakPoint):
n = 0
for i in seqRNA:
n += 1
for i in breakPoint:
if i == n:
seqRNA = seqRNA[n:] + ' ' + seqRNA[:n]
return seqRNA
The return string, however, is transposed out of order. Example:
>>> test = breakRNA('AAAAAAAAAAAAAAAAAAAAAAAAAAATTTTTGGGGGGGGCCCCCCCCCC', 5, 8, 14)
>>> test
>>> 'TTTTTGGGGGGGGCCCCCCCCCC AAAAA AAAAAAAA AAAAAAAAAAAAAA'
I am a day-1 beginner so any advice is appreciated. Thank you.
String are indexed like list in Python.
For example consider the following:
test_string = "azertyuiop"
print test_string[0] #will return 'a'
print test_string[0:2] #will return 'az'
So getting back to your problem:
def insert_space(string, integer):
return string[0:integer] + ' ' + string[integer:]
Hope this is what you are looking for
def breakRNA(seqRNA, *breakPoint):
seqRNAList = []
noOfBreakPoints = len(breakPoint)
for breakPt in range(noOfBreakPoints):
for index in breakPoint:
seqRNAList.append(seqRNA[:index])
seqRNA = seqRNA[index:]
break
return seqRNAList
test = breakRNA('AAAAAAAAAAAAAAAAAAAAAAAAAAATTTTTGGGGGGGGCCCCCCCCCC', 5, 8, 14)
print test
This will return you alist then you can create a string out of it using join function.
simbol = input('Enter a character:\n')
triangle_n = int(input('Enter triangle height:\n'))
print('')
for i in range (triangle_n ):
for j in range(i+1):
print(simbol [0],end=' ')
print()
string_name = string_name[starting index:ending index] + ' ' + string_name[starting index:ending index]
example:
product_rating = '4.56888 rating 256156 reviews'
product_rating = product_rating[0:3] + ' ' + product_rating[3:]
output
'4.5 6888 rating 256156 reviews'
If ending index is not mentioned its default value will be till the end of string.
Note indexing will start from 0 and 0:3 means it will take 0 to 2.