Question

Good day,

I need to extract portion of string which can looks like this:

"some_text MarkerA some_text_to_extract MarkerB some_text"
"some_text MarkerA some_text_to_extract"

I need to extract some_text_to_extract in both cases.
MarkerA, MarkerB – predefined text strings.

I tried this regexps, but with no luck:

".*\sMarkerA(.*)MarkerB.*" - does not work in case 2
".*\sMarkerA(.*)(?=MarkerB)?.*" - wrong result "some_text_to_extract MarkerB some_text" 
".*\sMarkerA(.*)(?:MarkerB)?.*" - does not work at all

Could you please help me with this issue?

Answer 1

Try:

".*\sMarkerA(.*?)(?=$|MarkerB)"

Test code:

#!/usr/bin/env python

tests = [
        ("some_text MarkerA some_text_to_extract MarkerB some_text"," some_text_to_extract "),
        ("some_text MarkerA some_text_to_extract"," some_text_to_extract")
        ]

import re
reg = re.compile(r".*\sMarkerA(.*?)(?=$|MarkerB)")

for (input,expected) in tests:
    mo = reg.match(input)
    assert mo is not None
    print mo.group(1),expected
    assert mo.group(1) == expected