How to use re.sub function for the following?

Question

i would like to substitute the below lines to,

ABC+::A1
CDE+:A1A1A1

Expected Output:

ABC+::A1
TIM+++2020:11:21:12:51+ZZZ
ABC++ADDEDTIME
CDE+:A1A1A1

I would like to add the following lines between the above two lines. Please note that from the above lines, A1/A1A1A1 is a variable will keep changing but the first three alpha character remains the same. Hence no matter what is mentioned after the colon (+::), the below two lines must be added,

Lines to be added

TIM+++2020:11:21:12:51+ZZZ
ABC++ADDEDTIME

Answer 1

We could make good use of re like this shown below:

import re
regex = r"^(ABC\+::[A-Z0-9]+\n)(?=^CDE\+:[A-Z0-9]+)"
test_str = ("ABC+::A1\n"
    "CDE+:A1A1A1")
subst = "\\1TIM+++2020:11:21:12:51+ZZZ\\nABC++ADDEDTIME\\n"

result = re.sub(regex, subst, test_str, 0, re.MULTILINE)
if result:
    print(result)

Regex Demo

Basically, the regex pattern matches ABC+::ALPHANUM{1, or more} followed by CDE+:ALPHANUM{1, or more} and substitutes the first match in brackets back, and adds line breaks and the new strings after it.