python - 如何计算列表项的出现？(How can I count the occurrences of a list item?)

Question

给定一个项目，我如何计算它在Python列表中的出现次数？

  ask by weakish translate from so

Answer 1

If you only want one item's count, use the count method:

(如果您只想要一项的计数，请使用count方法：)

>>> [1, 2, 3, 4, 1, 4, 1].count(1)
3

Don't use this if you want to count multiple items.

(如果要计数多个项目，请不要使用此选项。)

Calling count in a loop requires a separate pass over the list for every count call, which can be catastrophic for performance.

(循环调用count需要为每个count调用单独遍历列表，这可能会对性能造成灾难性影响。)

If you want to count all items, or even just multiple items, use Counter , as explained in the other answers.

(如果您要计算所有项目，甚至只是多个项目，请使用Counter ，如其他答案中所述。)