Invert keys and values of the original dictionary

Question

For example, I call this function by passing a dictionary as parameter:

>>> inv_map({\'a\':1, \'b\':2, \'c\':3, \'d\':2})
{1: [\'a\'], 2: [\'b\', \'         


        

Answer 1

You can probably use defaultdict or setdefault here.

def invertDictionary(orig_dict):
    result = {} # or change to defaultdict(list)
    for k, v in orig_dict.iteritems():
        result.setdefault(v, []).append(k)