如何允许用户在Python中过滤元组

Question

I currently have a dictionary which is structured like this:

{
    (foo, bar, baz): 1,
    (baz, bat, foobar): 5
}

Within this structure, the key is a tuple representing the entry's properties. Outside of the dictionary, I have another tuple:

(property1, property2, property3)

This maps directly to the keys of the dictionary. I would like the user to be able to input filters to get relevant keys within the dictionary, based on the property. Ideally, this would take the form of a dictionary as well. For example, if the user entered {property1: foo} , the program would return:

{
    (foo, bar, baz): 1
}

Answer 1

This is certainly possible, but my implementation was not nearly as clean as I hoped it would be. The basic approach is to construct an intermediate dictionary matcher which contains the tuple indices to be matched as keys and their corresponding strings (or what have you) as values.

def get_property_index(prop):
    try:
        if prop.startswith('property'):
            # given 'property6' returns the integer 5 (0-based index)
            return int(prop[8:]) - 1
        else:
            raise ValueError

    except ValueError:
        raise AttributeError('property must be of the format "property(n)"')

def filter_data(data, filter_map):
    matcher = {}
    for prop, val in filter_map.items():
        index = get_property_index(prop)
        matcher[index] = val

    filtered = {}
    for key, val in data.items():
        # checks to see if *any* of the provided properties match
        # if you want to check if *all* of the provided properties match, use "all"
        if any(key[index] == matcher[index] for index in matcher):
            filtered[key] = val

    return filtered

Some example usage is given below, it should match up with the requested usage.

data = {
    ('foo', 'bar', 'baz'): 1,
    ('foo', 'bat', 'baz'): 2,
    ('baz', 'bat', 'foobar'): 3
}

filter_map1 = {
    'property1': 'foo'
}

print filter_data(data, filter_map1)
# {('foo', 'bar', 'baz'): 1, ('foo', 'bat', 'baz'): 2}

filter_map2 = {
    'property2': 'bat'  
}

print filter_data(data, filter_map2)
# {('foo', 'bat', 'baz'): 2, ('baz', 'bat', 'foobar'): 3}

filter_map3 = {
    'property2': 'bar',
    'property3': 'foobar'
}

print filter_data(data, filter_map3)
# {('foo', 'bar', 'baz'): 1, ('baz', 'bat', 'foobar'): 3}