python – Reverse / invert a dictionary mapping

python – Reverse / invert a dictionary mapping

Python 3+:

inv_map = {v: k for k, v in my_map.items()}

Python 2:

inv_map = {v: k for k, v in my_map.iteritems()}

Assuming that the values in the dict are unique:

Python 3:

dict((v, k) for k, v in my_map.items())

Python 2:

dict((v, k) for k, v in my_map.iteritems())

python – Reverse / invert a dictionary mapping

If the values in my_map arent unique:

Python 3:

inv_map = {}
for k, v in my_map.items():
    inv_map[v] = inv_map.get(v, []) + [k]

Python 2:

inv_map = {}
for k, v in my_map.iteritems():
    inv_map[v] = inv_map.get(v, []) + [k]