python - 计算字符串中的运行次数

Question

我有一个看起来像这样的字符串：

string = 'TTHHTHHTHHHHTTHHHTTT'

我如何计算字符串中的运行次数以便得到，

5 次 T 运行和 4 次 H 运行

Answer 1

You can use a combination of itertools.groupby and collections.Counter:

>>> from itertools import groupby
>>> from collections import Counter
>>> strs = 'TTHHTHHTHHHHTTHHHTTT'
>>> Counter(k for k, g in groupby(strs))
Counter({'T': 5, 'H': 4})

itertools.groupby groups the item based on a key.(by default key is the items in the iterable itself)

>>> from pprint import pprint
>>> pprint([(k, list(g)) for k, g in groupby(strs)])
[('T', ['T', 'T']),
 ('H', ['H', 'H']),
 ('T', ['T']),
 ('H', ['H', 'H']),
 ('T', ['T']),
 ('H', ['H', 'H', 'H', 'H']),
 ('T', ['T', 'T']),
 ('H', ['H', 'H', 'H']),
 ('T', ['T', 'T', 'T'])]

Here first item is the key(k) based on which the items were grouped and list(g) is the group related to that key. As we're only interested in key part, so, we can pass k to collections.Counter to get the desired answer.

Answer 2

对于品种，一种re基于方法

import re
letters = ['H', 'T']
matches = re.findall(r'({})\1*'.format('|'.join(letters)), 'TTHHTHHZTHHHHTTHHHTTT')      
print matches
['T', 'H', 'T', 'H', 'T', 'H', 'T', 'H', 'T']
[(letter, matches.count(letter)) for letter in letters]
[('H', 4), ('T', 5)]