Question

I have a tuple of tuples and a tuple. I’m interested to know which elements of the first tuple match the second tuple (if any), considering partial matches too.

This is a filter function to demonstrate what I mean.

def f(repo):
    pattern = (None, None, '1.3')
    for idx, item in enumerate(pattern):
        if item != None and item != repo[idx]:
            return False
    return True

>>> repo = (('framework', 'django', '1.3'), ('cms', 'fein', '1.3'), ('cms', 'django-cms', '2.2'))
>>> filter(f, repo)
(('framework', 'django', '1.3'), ('cms', 'fein', '1.3'))

The filter is useless in this form because the pattern can’t be provided externally as an argument (I want to use the same function to check different inputs). Is there a way to fix this?

And, what could be another algorithm to embrace for a better approach to the original problem?

Answer 1

You can use a closure to bind the pattern into the function:

def matcher(pattern):
    def f(repo):
        return all(p is None or r == p for r, p in zip(repo, pattern))
    return f

>>> repo = (('framework', 'django', '1.3'), ('cms', 'fein', '1.3'), ('cms', 'django-cms', '2.2'))
>>> pattern = (None, None, '1.3')
>>> filter(matcher(pattern), repo)
(('framework', 'django', '1.3'), ('cms', 'fein', '1.3'))

I’ve also provided a different expression for comparing the tuples.