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
使用来自不同电子邮件平台的分隔符解析文本带来了这个问题的更大版本。它们通常有一个开始和一个停止。通配符的分隔符字符不断阻塞正则表达式。这里和其他地方都提到了分割的问题——哎呀，分隔符不见了。我突然想到使用replace()来让split()使用其他东西。代码块:
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)
其他回答
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)
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]
这是我之前在Daniweb中发布的代码片段:
# 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')
"""
s[len(start):-len(end)]
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!
