如何从符合特定条件的列表中返回对象-Python

Question

I'm Writing a search function where I'm searching through a list for matching Words or characters. It looks like

    def search(seq, db):
        return match(db, seq)

Where match is a recursive function which searches through the lists and returns a boolean value. How do I return a list with the matching objects instead of just True or False?

The match functions looks like this:

def match(seq, pattern):

    if not pattern:
        return not seq

    elif pattern[0] == '--':

        if match(seq, pattern[1:]):
            return True

        elif not seq:
            return False

        else:
            return match(seq[1:], pattern)

    elif not seq: 
        return False 

    elif pattern[0] == '&':
        return match(seq[1:], pattern[1:])

    elif seq[0] == pattern[0]:
        return match(seq[1:], pattern[1:])

    elif isinstance(seq[0], list):
        return match(seq[0], pattern)

    elif isinstance(pattern[0], list):
        return match(seq, pattern[0])

    else:
        return False

Answer 1

I don't really understand what your match function is doing. I'm guessing you're wanting the match function to return a list instead of a boolean value.

You can start by changing your base cases. Everywhere you see return False or return True instead say 'return [] or return [seq[0]] (assuming seq[0]` is a sensible thing to be returned in your list of matches).

With your return match(...) recursive cases you could return [seq[0]] + match(...) or something similar to add the current match (when applicable) to the listed returned by the recursive call.

This method of prepending lists is not particularly efficient, but I doubt that your concern now.