python - 我在 python 中有一个列表，其中包含许多名称，我想打印出每个名称出现的次数

Question

前任：

list = ['herp' , 'derp', 'foo' , 'derp', 'foo', 'foo' , 'foo']

我希望能够得到这个代码，以便我可以打印出来：

herp occurs 1 times.
derp occurs 2 times.
foo occurs 4 times.

最好的方法是什么？

Answer 1

使用collections.Counter()对象：

from collections import Counter

counts = Counter(lst)

for word, count in counts.most_common():
    print '{} occurs {} times'.format(word, count)

这具有按频率对单词进行排序的好处。如果您需要按字母顺序排序的单词，请对.items()结果进行排序：

import operator

for word, count in sorted(counts.items(), key=operator.itemgetter(1)):

演示：

>>> lst = ['herp' , 'derp', 'foo' , 'derp', 'foo', 'foo' , 'foo']
>>> from collections import Counter
>>> counts = Counter(lst)
>>> for word, count in counts.most_common():
...     print '{} occurs {} times'.format(word, count)
... 
foo occurs 4 times
derp occurs 2 times
herp occurs 1 times
>>> import operator
>>> for word, count in sorted(counts.items(), key=operator.itemgetter(1)):
...     print '{} occurs {} times'.format(word, count)
... 
herp occurs 1 times
derp occurs 2 times
foo occurs 4 times

Answer 2

使用collections.Counter

from collections import Counter

Counter(['herp' , 'derp', 'foo' , 'derp', 'foo', 'foo' , 'foo'])
# Counter({'foo': 4, 'derp': 2, 'herp': 1})

Answer 3

遍历您的列表并构建一个名称字典，并为每个字典条目增加一个计数器，以记录您遇到该名称的次数。