python - 将字符串向左旋转 n 个字符，特殊字符除外

Question

嗨，我需要帮助将字符串向左旋转 n 次，我已经这样做了:btw Strings 是字符串列表:

 finaltext = ""
 for i in strings:
    first = i[0 : n] 
    second = i[n :] 
    i = second + first
    finaltext += i

但是，我不知道如何执行此操作，以便在给定的字符串中说:“实习生”，空格或任何特殊字符都不会移动。

s1 = "The intern"

现在我的输出是: tern中

我想要的输出: 埃恩·埃登

有什么想法吗？我目前创建了一个函数，指示字符串中的特殊字符及其索引，我在 for 循环中使用它来知道当前字符是特殊字符，但是当涉及到旋转时，我将如何避免该字符

Answer 1

一个有趣的问题。如何旋转字符串同时忽略特定字符？

在这里，我们删除、旋转、重新插入字符。

给定

import collections as ct


def index(s):
    """Return a reversed dict of (char, [index, ...]) pairs."""
    dd = ct.defaultdict(list)
    for i, x in enumerate(s):
        dd[x].append(i)
    return dd


s1 = "The intern"
s2 = "Hello world!"

代码

def rotate(s, n=0, ignore=""):
    """Return string of rotated items, save ignored chars."""
    s0 = s[:]

    # Remove ignored chars
    for ig in ignore:
        s = s.replace(ig, "")

    # Rotate remaining string, eqiv. to `res = s[-n:] + s[:-n]`
    tail = s[-n:]
    head = ""

    for c in s[:-n]:         
        head += c    
    res = tail + head


    # Reinsert ignored chars
    if ignore:
        res = list(res)
        lookup = index(s0)
        for ig in ignore:
            for idx in lookup[ig]:
                res.insert(idx, ig)
        res = "".join(res)
    return res

测试

assert rotate(s1, n=0, ignore="") == "The intern"
assert rotate(s1, n=1, ignore="") == "nThe inter"
assert rotate(s1, n=1, ignore=" ") == "nTh einter"
assert rotate(s1, n=3, ignore=" ") == "ern Theint"

assert rotate(s2, n=12, ignore="") == "Hello world!"
assert rotate(s2, n=1, ignore="") == "!Hello world"
assert rotate(s2, n=1, ignore="H !") == "Hdell oworl!"
assert rotate(s2, n=1, ignore="!") == "dHello worl!"