Python，使用列表，找到最大序列长度

Question

例如测试列表:

test_list = ['a', 'a', 'a', 'b', 'b', 'a', 'c', 'b', 'a', 'a']

对于这个例子，我需要使用什么工具或算法来获得最大序列数:

'a' = 3
'b' = 2
'c = 1

Answer 1

使用 dict 来跟踪最大长度，并且 itertools.groupby按连续值对序列进行分组:

from itertools import groupby

max_count = {}

for val, grp in groupby(test_list):
    count = sum(1 for _ in grp)
    if count > max_count.get(val, 0):
        max_count[val] = count

演示:

>>> from itertools import groupby
>>> test_list = ['a', 'a', 'a', 'b', 'b', 'a', 'c', 'b', 'a', 'a']
>>> max_count = {}
>>> for val, grp in groupby(test_list):
...     count = sum(1 for _ in grp)
...     if count > max_count.get(val, 0):
...         max_count[val] = count
... 
>>> max_count
{'a': 3, 'c': 1, 'b': 2}