Python cookbook (data structure and algorithm) dictionary-related computing example, pythoncookbook

Python cookbook (data structure and algorithm) dictionary-related computing example, pythoncookbook

This example describes the computation problems related to the Python cookbook (data structure and algorithm) dictionary. We will share this with you for your reference. The details are as follows:

Problem:Perform Various calculations (such as minimum, maximum, and sorting) on the data in the dictionary ).

Solution:Exploitationzip()Convert the dictionary's key-value pairs into a value-key pair sequence.

For example, the following dictionary stores the stock name and the corresponding price:

>>> Prices = {'acme ': 45.23, 'aap': 612.78, 'ibm': 205.55, 'hpq': 37.20, 'fb ': 10.75 }>>> prices {'hpq': 37.2, 'ibm ': 205.55, 'fb': 10.75, 'acme ': 45.23, 'aap ': 612.78 }>>> min_price = min (zip (prices. values (), prices. keys () # note the order of parameters in zip (x, y)> max_price = max (zip (prices. values (), prices. keys () >>>> min_price (10.75, 'fb ') >>> max_price (612.78, 'aap') >>>> 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')]> min_price2 = min (zip (prices )) # incorrect usage >>> min_price2 ('aapl ',) >>> max_price2 = max (zip (prices )) # incorrect usage >>> max_price2 ('ibm ',) >>> min_price3 = min (zip (prices. keys (), prices. values () # The zip () parameter order is incorrect. The obtained value is incorrect. >>> min_price3 ('aapl ', 612.78) >>> max_price3 = max (zip (prices. keys (), prices. values () # incorrect zip () parameter order, incorrect value obtained >>> max_price3 ('ibm ', 205.55) >>>

Note thatzip()An iterator is created and its content can only be consumed once. For example:

>>> pirces_and_names=zip(prices.values(), prices.keys())>>> pirces_and_names<zip object at 0x023BDFA8>>>> min(pirces_and_names)(10.75, 'FB')>>> max(pirces_and_names)Traceback (most recent call last): File "<pyshell#25>", line 1, in <module> max(pirces_and_names)ValueError: max() arg is an empty sequence>>>

Note:When comparing (value, key) pairs, multiple entries may have the same value. In this case, the key is used as the basis for determining the result.

>>> prices={'AAA':45.23,'ZZZ':45.23}>>> min(zip(prices.values(), prices.keys()))(45.23, 'AAA')>>> max(zip(prices.values(), prices.keys()))(45.23, 'ZZZ')>>>

(The code is from Python Cookbook.)