Merges two dictionaries recursively

merge_dict.py

import collections

def merge_dict(d1, d2):
    for k,v2 in d2.items():
        v1 = d1.get(k) # returns None if v1 has no value for this key
        if ( isinstance(v1, collections.Mapping) and
                isinstance(v2, collections.Mapping) ):
            merge_dict(v1, v2)
        else:
            d1[k] = v2