I have a function that I use to convert a list of dictionaries into a list of tuples, similar to itertools.groupby() would do in an ideal world. The goal is to make a list of {unique-dict} => [list of values]. I'm having a hard time explaining it, so I hope the example makes it clear.

I couldn't find a thing on google, so I wrote it pretty quickly, and I am wondering if there is a better way to do this (or a standard library even)

• Naming things is hard... what is a better one?
• This is a task I performed fairly often when receiving user input
• The keys in each dict may not be consistent (some may be missing)
• It is OK to destroy or mangle the original input list & items
• Validation is done before calling, so 'key_field' is always present
• It is expected that values can be duplicated in the list.
• { status: 1 } => [1,2,3,4,1,2] is ok, if the values are actually present twice.

Simple little python function:

def group_by_excluding_key(list_of_dicts, key_field):
    """
    Takes a list of `dict` items and groups by ALL KEYS in the dict EXCEPT the key_field.
    :param list_of_dicts: List of dicts to group
    :param key_field: key field in dict which should be excluded from the grouping
    """

    output = []

    for item in list_of_dicts:

        found = False
        search_group = {k: v for k, v in item.items() if k != key_field}
        item_value = item[key_field]

        for existing_group, found_keys in output:
            if existing_group.viewitems() == search_group.viewitems():
                found_keys.append(item_value)
                found = True

        if not found:
            output.append((search_group, [item_value]))

    return output

Example Input/Output

from pprint import pprint

data = [
    {'id': 1, 'status': 1, 'product': 1},
    {'id': 2, 'status': 1, 'product': 1},
    {'id': 7, 'status': 1, 'product': 2},
    {'id': 9, 'status': 1, 'product': 2},
    {'id': 3, 'status': 1, 'product': 1},
    {'id': 4, 'status': 1, 'product': 1},
    {'id': 8, 'status': 1, 'product': 2},
    {'id': 1, 'status': 1, 'product': 1},
]

results = group_by_excluding_key(data, 'id')

pprint(results)

# [({u'product': 1, u'status': 1}, [1, 2, 3, 4, 1]),
#  ({u'product': 2, u'status': 1}, [7, 9, 8])]