python - 如何在 Python 中获取字符的位置？

Question

如何在 Python 中获取字符在字符串中的位置？

Answer 1

有两个字符串方法，find() 和 index()。两者之间的区别在于找不到搜索字符串时会发生什么。 find() 返回 -1 并且 index() 引发 ValueError。

使用 find()

>>> myString = 'Position of a character'
>>> myString.find('s')
2
>>> myString.find('x')
-1

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使用 index()

>>> myString = 'Position of a character'
>>> myString.index('s')
2
>>> myString.index('x')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: substring not found

---

来自 Python manual

string.find(s, sub[, start[, end]])
Return the lowest index in s where the substring sub is found such that sub is wholly contained in s[start:end]. Return -1 on failure. Defaults for start and end and interpretation of negative values is the same as for slices.

还有:

string.index(s, sub[, start[, end]])
Like find() but raise ValueError when the substring is not found.