为什么str.count（''）和len（str）给出不同的输出？ [英] Why are str.count('') and len(str) giving different output?

问题描述

看下面的代码，请解释为什么 str.count（''）方法和 len（str）函数给出两个不同的输出。

Look at following code and please explain why the str.count('') method and len(str) function is giving two different outputs.

a=''
print(len(a))
print(a.count(''))

输出：

0
1

推荐答案

str.count（）计算子字符串的非重叠出现次数：

str.count() counts non-overlapping occurrences of the substring:

返回子字符串 sub 不重复出现的次数。

恰好有一个这样的地方，子字符串''出现在字符串''中：就在开头。因此，计数应该返回 1 。

There is exactly one such place where the substring '' occurs in the string '': right at the start. So the count should return 1.

通常，空字符串将匹配在给定字符串的所有位置处，包括开始和结束位置，因此计数应始终为长度加上1：

Generally speaking, the empty string will match at all positions in a given string, including right at the start and end, so the count should always be the length plus 1:

>>> (' ' * 100).count('')
101

这是因为空字符串被认为存在于字符串的所有字符之间；对于字符串长度2，有3个空字符串；

That's because empty strings are considered to exist between all the characters of a string; for a string length 2, there are 3 empty strings; one at the start, one between the two characters, and one at the end.

所以是的，结果是不同的，而且完全正确。

So yes, the results are different and they are entirely correct.

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