You can put comments like you normally would anywhere in a python script. But note that you can only put single line comments using #. Multiline comments act like strings and you cannot put just a string in between definition of a dict. For example, the following declaration is perfectly valid:
testItems = { 'TestOne': 'Hello', # 'TestTwo': None, }
But the following is not:
testItems = { 'TestOne': 'Hello', """ Some random multiline comment """ }