Python:索引子字符串中的位置

Question

我正在尝试创建一个程序，该程序将列出子字符串在父字符串中出现的位置。例如，假设我们在父字符串“abcabcabcabcabcabca”中搜索“bc”，程序将返回 1、4、7、10、13、16。

到目前为止，我一直在使用:

import string

def subStringMatchExact():
    print "This program will index the locations a given sequence"
    print "occurs within a larger sequence"
    seq = raw_input("Please input a sequence to search within: ")
    sub = raw_input("Please input a sequence to search for: ")
    n = 0
    for i in seq:
        x = string.find(seq, sub [n:])
        print x
        n = x + 1

我还尝试用 string.index 运算符替换 string.find。任何建议将不胜感激。

Answer 1

只需调用 .find()在输入字符串本身上。如果未找到匹配项，它将返回匹配项的位置或 -1。它还需要一个start 参数，因此您可以查找下一个 匹配项:

def subStringMatchExact():
    print "This program will index the locations a given sequence"
    print "occurs within a larger sequence"
    seq = raw_input("Please input a sequence to search within: ")
    sub = raw_input("Please input a sequence to search for: ")

    positions = []
    pos = -1
    while True:
        pos = seq.find(sub, pos + 1)  # start searching *beyond* the previous match
        if pos == -1:   # Not found
            break
        positions.append(pos)
    return positions