在 python 3 中使用正则表达式查找 substring 的最佳方法

Question

I was trying to find out the best way to find the specific substring in key value pair using re for the following:

some_string-variable_length/some_no_variable_digit/some_no1_variable_digit/some_string1/some_string2
eg: aba/101/11111/cde/xyz or aaa/111/1119/cde/xzx or ada/21111/5/cxe/yyz

here everything is variable and what I was looking for is something like below in key value pair:

`cde: 2` as there are two entries for cde

cxe: 1 as there is only one cxe

Note: everything is variable here except / . ie cde or cxe or some string will be there exactly after two / in each case

input:aba/101/11111/cde/xyz/blabla
output: cde:xyz/blabla
input: aaa/111/1119/cde/xzx/blabla
output: cde:xzx/blabla
input: aahjdsga/11231/1119/gfts/sjhgdshg/blabla
output: gfts:sjhgdshg/blabla

If you notice here, my key is always the first string after 3rd / and value is always the substring after key

Answer 1

Here are a couple of solutions based on your description that "key is always the first string after 3rd / and value is always the substring after key". The first uses str.split with a maxsplit of 4 to collect everything after the fourth / into the value. The second uses regex to extract the two parts:

inp = ['aba/101/11111/cde/xyz/blabla',
        'aaa/111/1119/cde/xzx/blabla',
        'aahjdsga/11231/1119/gfts/sjhgdshg/blabla'
        ]

for s in inp:
    parts = s.split('/', 4)
    key = parts[3]
    value = parts[4]
    print(f'{key}:{value}')

import re

for s in inp:
    m = re.match(r'^(?:[^/]*/){3}([^/]*)/(.*)$', s)
    if m is not None:
        key = m.group(1)
        value = m.group(2)
        print(f'{key}:{value}')

For both pieces of code the output is

cde:xyz/blabla
cde:xzx/blabla
gfts:sjhgdshg/blabla

Answer 2

Try (?<?\S)[^\s/]*(::/[^\s/]*){2}/([^\s/]*)

demo

---

Try new per commnt

(?<?\S)[^\s/]*(:?/[^\s/]*){2}/([^\s/]*)(:?/(\S*))?

demo2

Answer 3

Others have already posted various regexes; a more broad question — is this problem best solved using a regex? Depending on how the data is formatted overall, it may be better parsed using

• the .split('/') method on the string ; or
• csv.reader(..., delimiter='/') or csv.DictReader(..., delimiter='/') in the csv module.