如何按值对Counter排序? - Python [英] How to sort Counter by value? - python

问题描述

除了进行反向列表理解的列表理解之外，还有一种Python的方法可以按值对Counter进行排序吗?如果是这样，它比这快:

Other than doing list comprehensions of reversed list comprehension, is there a pythonic way to sort Counter by value? If so, it is faster than this:

>>> from collections import Counter
>>> x = Counter({'a':5, 'b':3, 'c':7})
>>> sorted(x)
['a', 'b', 'c']
>>> sorted(x.items())
[('a', 5), ('b', 3), ('c', 7)]
>>> [(l,k) for k,l in sorted([(j,i) for i,j in x.items()])]
[('b', 3), ('a', 5), ('c', 7)]
>>> [(l,k) for k,l in sorted([(j,i) for i,j in x.items()], reverse=True)]
[('c', 7), ('a', 5), ('b', 3)

推荐答案

使用它将以最有效的方式进行；如果您要求输入前N个而不是所有值，则使用heapq而不是直接排序:

It'll do so in the most efficient manner possible; if you ask for a Top N instead of all values, a heapq is used instead of a straight sort:

>>> x.most_common(1)
[('c', 7)]

除计数器外，始终可以根据key函数来调整排序. .sort()和sorted()都可调用，可用于指定对输入序列进行排序的值. sorted(x, key=x.get, reverse=True)将为您提供与x.most_common()相同的排序，但是仅返回键，例如:

Outside of counters, sorting can always be adjusted based on a key function; .sort() and sorted() both take callable that lets you specify a value on which to sort the input sequence; sorted(x, key=x.get, reverse=True) would give you the same sorting as x.most_common(), but only return the keys, for example:

>>> sorted(x, key=x.get, reverse=True)
['c', 'a', 'b']

或者您可以仅对给定的(key, value)对值进行排序:

or you can sort on only the value given (key, value) pairs:

>>> sorted(x.items(), key=lambda pair: pair[1], reverse=True)
[('c', 7), ('a', 5), ('b', 3)]

有关更多信息，请参见 Python排序方法.

See the Python sorting howto for more information.

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