我如何找到两个子字符串('123STRINGabc' -> '字符串')之间的字符串?
我现在的方法是这样的:
>>> start = 'asdf=5;'
>>> end = '123jasd'
>>> s = 'asdf=5;iwantthis123jasd'
>>> print((s.split(start))[1].split(end)[0])
iwantthis
然而，这似乎非常低效且不符合python规则。有什么更好的方法来做这样的事情吗?
忘了说: 字符串可能不是以start和end开始和结束的。他们可能会有更多的字符之前和之后。
当前回答
这本质上是cji的答案——7月30日10日5:58。 我更改了try except结构，以便更清楚地说明导致异常的原因。
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]
其他回答
只是把OP自己的解决方案转换成一个答案:
def find_between(s, start, end):
return (s.split(start))[1].split(end)[0]
这些解决方案假设起始字符串和最终字符串是不同的。下面是当初始和最终指示符相同时，我用于整个文件的解决方案，假设整个文件是使用readlines()读取的:
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)
例子:
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)
给:
A NEWT?
I GOT BETTER!
我的方法是，
find index of start string in s => i
find index of end string in s => j
substring = substring(i+len(start) to j-1)
下面是一个函数，我做了返回一个字符串(s)之间的字符串string1和string2搜索列表。
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
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" )
给:
123STRING
STRINGabc
我认为应该注意的是-根据需要的行为，您可以混合使用index和rindex调用，或者使用上述版本之一(它相当于regex(.*)和(.*?)组)。
