'too many values to unpack', iterating over a dict. key=>string, value=>list

Python 3

for field, possible_values in fields.items():
    print(field, possible_values)

Since Python 3 iteritems() is no longer supported. Use items() instead.

You need to use something like iteritems.

for field, possible_values in fields.iteritems():
    print field, possible_values

See this answer for more information on iterating through dictionaries, such as using items(), across python versions.

For Python 3.x iteritems has been removed. Use items instead.

for field, possible_values in fields.items():
    print(field, possible_values)