Python在索引后找到第一个出现的字符

Question

我试图获取指定索引后字符串​​中出现的第一个字符的索引。例如：

string = 'This + is + a + string'

# The 'i' in 'is' is at the 7th index, find the next occurrence of '+'
string.find_after_index(7, '+')

# Return 10, the index of the next '+' character
>>> 10

Answer 1

Python是如此可预测：

>>> string = 'This + is + a + string'
>>> string.find('+',7)
10

结帐help(str.find)：

find(...)
    S.find(sub[, start[, end]]) -> int

    Return the lowest index in S where substring sub is found,
    such that sub is contained within S[start:end].  Optional
    arguments start and end are interpreted as in slice notation.

    Return -1 on failure.

同样适用于str.index，但在找不到子字符串时，raise ValueError代替-1。

Answer 2

您可以使用：

start_index = 7
next_index = string.index('+', start_index)

Answer 3

string.find('+', 7)

阅读the documentation。

Answer 4

In [1]: str.index?
Docstring:
S.index(sub[, start[, end]]) -> int

Like S.find() but raise ValueError when the substring is not found.
Type:      method_descriptor

In [2]: string = 'This + is + a + string'

In [3]: string.index('+', 7)
Out[3]: 10

Answer 5

nullglob

上面的代码将从您提供的索引for i in range(index, len(string)): if string[i] == char: print(i) 循环到字符串index的长度。然后，如果字符串的索引等于您要查找的字符len(string)，那么它将打印索引。

你可以将它放在一个函数中并传入，字符串，索引和字符，然后返回i。