Name Error: name 'Stockton' is not defined

[Yoriz]

As the error is saying 'Stockton' is not defined anywhere in the code shown neither is Rockwall, Joliet, Atlanta or York.
Did you mean for them to string values? add quotes to them.

data = {None: {
    'e': {'Stockton': 325000, 'Rockwall': 50000, 'Joliet': 350000,
          'Atlanta': 450000, 'York': 170000}}}