如何从字符串中去除标点符号并在同一索引处重新添加？

Question

我想让程序这样做：假设我的字符串是 "This is 'Cambridge University' for example." 它会保留每个单词的首字母和尾字母，然后把中间的字母打乱，但前提是这个单词的长度要大于3个字母。我的问题是，当单词前面或后面有标点符号时，程序会错误地打乱这些单词。我需要它在打乱时，确保标点符号保持在正确的位置，同时保留单词的首尾字母，并把中间的字母打乱，如果有标点符号的话，还要把它加到最后。有没有什么好的想法？

def scramble_word(word_str):
char = ".,!?';:"
import random
if len(word_str) <= 3:
    return word_str + ' '
else:
    word_str = word_str.strip(char)
    word_str = list(word_str)
    scramble = word_str[1:-1]
    random.shuffle(scramble)
    scramble = ''.join(scramble)
    word_str = ''.join(word_str)
    new_word = word_str[0] + scramble + word_str[-1]
    return new_word + ' '

Answer 1

用正则表达式来做这件事非常简单：

import re
import random

s = ('Pitcairn Islands, Saint Helena, '
     'Ascension and Tristan da Cunha, '
     'Saint Kitts and Nevis, '
     'Saint Vincent and the Grenadines, Singapore')

reg = re.compile('(?<=[a-zA-Z])[a-zA-Z]{2,}(?=[a-zA-Z])')

def ripl(m):
    g = list(m.group())
    random.shuffle(g)
    return ''.join(g)

print reg.sub(ripl,s)

结果

Piictran Islands, Sanit Heelna, Asnioecsn and Tiastrn da Cunha, Sniat Ktits and Neivs, Snait Vnnceit and the Giearndens, Snoiaprge

Answer 2

使用正则表达式：

import random
import re

random.seed(1234) #remove this in production, just for replication of my results

def shuffle_word(m):
    word = m.group()
    inner = ''.join(random.sample(word[1:-1], len(word) - 2))
    return '%s%s%s' % (word[0], inner, word[-1])
    
s = """This is 'Cambridge University' for example."""

print re.sub(r'\b\w{3}\w+\b', shuffle_word, s)

这段代码的输出是

Tihs is 'Cadibrgme Uinrtvsiey' for exlampe.

re.sub 这个函数让你可以传入一个函数（这个函数接受一个正则匹配对象），而不是直接传入一个替换的字符串。

编辑 - 不使用正则表达式

from StringIO import StringIO

def shuffle_word(m):
    inner = ''.join(random.sample(m[1:-1], len(m) - 2))
    return '%s%s%s' % (m[0], inner, m[-1])

def scramble(text)
    sio = StringIO(text)
    accum = []
    start = None
    while sio.tell() < sio.len:
        char = sio.read(1)
        if start is None:
            if char.isalnum():
                start = sio.tell() - 1
            else:
                accum.append(char)
        elif not char.isalnum():
            end = sio.tell() - 1
            sio.seek(start)
            accum.append(shuffle_word(sio.read(end - start)))
            print accum[-1]
            start = None
    else:
        if start is not None:
            sio.seek(start)
            word = sio.read()
            if len(word) > 3:
                accum.append(shuffle_word(sio.read()))
            else:
                accum.append(word)
    
    return ''.join(accum)

s = """This is 'Cambridge University' for example."""
print scramble(s)