Reference : https://wiki.python.org/moin/Generators

keys.py

# <------------------------NORMAL FUNCTION -------------------------------->

        # # Build and return a list
        # def getKeys(data):
        #     return list(data.keys())

        # obj = { 'bar': "hello", 'baz': "world" }
        # keys_list = getKeys(obj)

# <------------------------BEHIND THE SCENE ------------------------------->
    # # Using the generator pattern (an iterable)
    #     class getKeys(obj):
    #         print(obj.keys())
    #         def __init__(self, obj):
    #             self.obj = obj

    #         def __iter__(self):
    #             return self

    #         # Python 3 compatibility
    #         def __next__(self):
    #             return self.next()

    #         def next(self):
    #             if self.obj:
    #                 return list(obj.keys())
    #             else:
    #                 raise ValueError('Dear Lord,Gimme object')


    #     data = {'bar': "hello", 'baz': "world"}
    #     keys_list = getKeys(data)
    #     print(keys_list)

# <------------------------GENERATOR PATTERN ------------------------------->

# a generator that yields items instead of returning a list


def getKeys(obj):
    if (type(obj) is dict):
        yield [obj.keys()]
    else:
        raise ValueError('Dear Lord,Gimme object')

data = {'bar': "hello", 'baz': "world"}
keys_list = getKeys(data)
print(list(keys_list))