如何使用 Python 在字符串中找到重叠序列的数量? [英] How can I find the number of overlapping sequences in a String with Python?

问题描述

我有一个很长的序列，我想知道一些子序列在这个序列中出现的频率.

I have a long sequence, and I would like to know how often some sub-sequences occur in this sequence.

我知道string.count(s, sub)，但是它只计算非重叠序列.

I know string.count(s, sub), but it only counts non-overlapping sequences.

是否存在类似的功能也计算重叠序列?

Does a similar function which also counts overlapping sequences exist?

推荐答案

作为编写自己的搜索功能的替代方法，您可以使用 re 模块:

As an alternative to writing your own search function, you could use the re module:

In [22]: import re

In [23]: haystack = 'abababa baba alibababa'

In [24]: needle = 'baba'

In [25]: matches = re.finditer(r'(?=(%s))' % re.escape(needle), haystack)

In [26]: print [m.start(1) for m in matches]
[1, 3, 8, 16, 18]

上面打印出所有(可能重叠)匹配项的起始位置.

The above prints out the starting positions of all (potentially overlapping) matches.

如果您只需要计数，以下应该可以解决问题:

If all you need is the count, the following should do the trick:

In [27]: len(re.findall(r'(?=(%s))' % re.escape(needle), haystack))
Out[27]: 5

这篇关于如何使用 Python 在字符串中找到重叠序列的数量?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！