按城市分别算出的总额

运行下面的 Python 3 程序，填写结果。

orders = [{"city": "北京", "amount": 120},
          {"city": "上海", "amount": 80},
          {"city": "北京", "amount": 200},
          {"city": "广州", "amount": 150}]
totals = {}
for o in orders:
    c = o["city"]
    totals[c] = totals.get(c, 0) + o["amount"]
print(totals)