字典運(yùn)算
問(wèn)題
在數(shù)據(jù)字典中執(zhí)行一些計(jì)算操作（比如求最小值、最大值锭弊、排序）堪澎？
解決
對(duì)字典值執(zhí)行計(jì)算操作，通常需要使用zip函數(shù)將鍵和值反轉(zhuǎn)過(guò)來(lái)
>>> prices = {
... 'ACME': 45.23,
... 'AAPL': 612.78,
... 'IBM': 205.55,
... 'HPQ': 37.20,
... 'FB': 10.75
... }
>>>
>>>
>>>
>>>
>>> min_price = min(zip(prices.values(), prices.keys()))
>>> min_price
(10.75, 'FB')
>>> max_price = max(zip(prices.values(), prices.keys()))
>>> max_price
(612.78, 'AAPL')
還可以用zip和sorted函數(shù)
>>> prices_sorted = sorted(zip(prices.values(), prices.keys()))
>>> prices_sorted
[(10.75, 'FB'), (37.2, 'HPQ'), (45.23, 'ACME'), (205.55, 'IBM'), (612.78, 'AAPL')]
注意
zip函數(shù)創(chuàng)建的是一個(gè)只能訪問(wèn)一次的迭代器
>>> prices_and_names = zip(prices.values(), prices.keys())
>>> print(min(prices_and_names)) # OK
(10.75, 'FB')
>>> print(max(prices_and_names))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: max() arg is an empty sequence
