In python how to print a character before a matching pattern that occur multiple times?

I have a stringified data from which I’m trying to print a character that occurs before a matching pattern. This matching pattern will occur multiple times so the result can also be a list of characters

E.g

Stringified data is [[1, "[{\"name\": \"john\", \"id\": \"1\"}]", [2, "[{\"name\": \"john\", \"id\": \"1\"}]"]

The matching pattern from the data will be , "[

The Expected result is 1 2

As we can see the charecter 1 and 2 is printed before each occurance of , "[

>Solution :

Purely on the basis of what’s asked in the question (and not wondering WHY?) one could do this:

astring = '[[1, "[{\"name\": \"john\", \"id\": \"1\"}]", [2, "[{\"name\": \"john\", \"id\": \"1\"}]"]'

pattern = ', "['

offset = 0
pchars = []

while (index := astring[offset:].find(pattern)) >= 0:
    if offset + index > 0:
        pchars.append(astring[offset+index-1])
    offset += index + 1

print(*pchars)

Output:

1 2