python - 为替换 split () 而构建的函数的意外行为

Question

我写了一个比内置函数 split() 表现更好的函数(我知道它不是惯用的 python，但我尽力了)，所以当我传递这个参数时:

better_split("After  the flood   ...  all the colors came out."," .")

我预料到这个结果:

['After', 'the', 'flood', 'all', 'the', 'colors', 'came', 'out']

然而，令人惊讶的是，该函数会导致(对我而言)无法理解的行为。当它到达最后两个词时，它不会抑制更多的 ''，而不是将“cam”和“out”添加到结果列表中，而是将其添加到“came out”中，因此，我得到了这个:

['After', 'the', 'flood', 'all', 'the', 'colors', 'came out']

有更多经验的人明白为什么会这样吗？提前感谢您的帮助!

def better_split(text,markersString):
markers = []
splited = []
for e in markersString:
    markers.append(e)    
for character in text:
    if character in markers:
        point = text.find(character)
        if text[:point] not in character:
            word = text[:point]
            splited.append(word)            
            while text[point] in markers and point+1 < len(text):
                point = point + 1
            text = text[point:]                   
print 'final splited = ', splited

better_split("This is a test-of the,string separation-code!", ",!-")

better_split("洪水过后……所有的颜色都出来了。",".")

split() 多重分离如果您正在寻找具有多重分离的 split() ，请参阅: Split Strings with Multiple Delimiters?

我找到的没有 import re 的最佳答案是:

def my_split(s, seps):
    res = [s]
    for sep in seps:
        s, res = res, []
        for seq in s:
            res += seq.split(sep)
    return res

Answer 1

问题在于:

    for character in text:

正在遍历初始字符串中的字符 — text 的原始值 — 同时:

        point = text.find(character)

在当前字符串中搜索分隔符 — text 的当前值。因此，您的那部分功能是在您一次处理一个定界符的假设下运行的；也就是说，它假设每当您在 original text 的循环中遇到定界符时，它就是 current< 中的第一个定界符/em> 文本。

同时，这:

            while text[point] in markers and point+n < len(text):
                point = point + 1
            text = text[point:]

用于一次删除多个分隔符；它的目标是删除一系列连续的定界符。这违反了上述代码一次只处理一个定界符的假设。

所以处理过程是这样的:

  [After  the flood   ...  all the colors came out.]
handling first space after "After":
  [After] [the flood   ...  all the colors came out.]
handling second space after "After":
  [After] [the] [flood   ...  all the colors came out.]
handling space after "the":
  [After] [the] [flood] [all the colors came out.]
handling first space after "flood":
  [After] [the] [flood] [all] [the colors came out.]
handling second space after "flood":
  [After] [the] [flood] [all] [the] [colors came out.]
handling third space after "flood":
  [After] [the] [flood] [all] [the] [colors] [came out.]
handling first period of the "...":
  [After] [the] [flood] [all] [the] [colors] [came out] []
-- text is now empty, no more splitting happens

如您所见，您处理的分隔符最终不会成为您拆分的分隔符。

解决方案只是删除让您一次跳过多个定界符的逻辑——也就是说，改变这个:

            while text[point] in markers and point+n < len(text):
                point = point + 1
            text = text[point:]

对此: text = text[(point + 1):]

相反，在将 word 添加到 splited 之前，确保它是非空的:

            if len(word) > 0:
                splited.append(word)