Python在列表中获取嵌套的字典值

Question

How do I get the start and end values in a dictionary named my_dict with this format:

import pprint
pprint.pprint(my_dict)

{'metadata': [{'filename': 'this_is_a_filename',
                  'filepath': 'this_is_a_filepath',
                  'location': 'this_is_a_location',
                  'time': {'end': 1489787859.905748,
                           'start': 1489787843.980593},
                  'place':
                  etc...

Where: my_dict is a dictionary metadata is a dictionary in my_dict time is a dictionary in a list whose index can change

I've tried:

for key in my_dict['metadata'][0]:
    if key == "time":
        print key("end")

but key is a string not an object so key("end") does not work. I've searched everything and tried for hours but cannot figure this out.

EDIT:

The user Dan answered correctly below within less than 3 minutes of asking the question :)

for d in my_dict.get('metadata', []):
    t = d.get('time', {})
    print t.get('end')
    print t.get('start')

Answer 1

for d in my_dict.get('metadata', []):
    t = d.get('time', {})
    print t.get('end')
    print t.get('start')