[lomkiri]

I found a better way for the function, with the property lastindex :

def replace(match, number, file_name, metadata, dictionaries, data, functions, *args, **kwargs):
    repl = ["Mick", "Kieth", "Ronnie", "Charlie"]
    idx = match.lastindex
    return repl[idx -1]
    
    # or, if you prefer safer : return repl[idx -1] if idx <= len(repl) else match[0]

Another way, with a dict:

def replace(match, number, file_name, metadata, dictionaries, data, functions, *args, **kwargs):
    equiv = {"John": "Mick", "Paul": "Kieth", "George": "Ronnie", "Ringo": "Charlie"}
    m = match[0]
    return equiv.get(m, m)    # if "m" is not in the dict, leave the text untouched

In both cases, it is possible to load the list or the dict in the function from a json file instead of defining it as a variable, maybe it was what you were thinking about? In that case, the function doesn't need to be modified at each use, only the regex and the json file.