如何使用正则表达式正确解析逗号分隔的行 [英] How to parse comma separated line correctly with regex

问题描述

试图用正则表达式解析逗号分隔的行，但结果不一致:

Trying to parse comma separated line with regex, but getting inconsistent results:

正则表达式:([[^，] *)，?

实际值在匹配组1中(不包括逗号).

The actual value is in match group 1 (excludes the comma).

预期结果:

a,,b  -> 3 matches
a,,b, -> 4 matches
a,,,b -> 4 matches

匹配数是逗号数+ 1.

The number of matches is the number of commas + 1.

问题在于即使没有逗号，正则表达式也会在末尾匹配，因此获取:

The problem is the regex matches at the end even if there is no comma, so getting:

a,,b  -> 4 matches
a,,b, -> 4 matches

即使这些行具有不同数量的值，它们都返回4个匹配项.

Both return 4 matches, even though the lines have a different number of values.

是否可以修正正则表达式，使匹配数为值的数量(逗号+ 1)，而无需在代码中更正结果?

Is it possible to fix the regex so the number of matches is the number of values (commas + 1) without correcting the results in code?

推荐答案

简介

您的正则表达式似乎在某些位置不匹配任何字符，并且只是一种断言(断言您的组中没有匹配的字符，并且后面没有逗号 ，这很完美)根据您的正则表达式有效).

Brief

It seems your regex is not matching any characters in some locations and working as a sort of assertion (asserting that no character is matched in your group and not followed by a comma ,, which is perfectly valid according to your regex).

此答案是一个 fix ，它允许您匹配1个或多个任意非逗号，字符，或者断言零宽度匹配的断言-同时声明该位置之前是逗号 .

This answer is a fix that allows you to match 1 or more of any non-comma , character, or an assertion for a zero-width match all-the-while asserting the position as being preceded by a comma ,.

执行此操作的最佳方法是使用字符串函数在，上拆分字符串，但是此方法也可以使用.

The best way to go about this would be to split the string on , using a string function, but this method also works.

在此处查看正在使用的正则表达式

([^,\v]+|(?<=,))(?=,|$)

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说明

• ([[^，\ v] + |(?< =，))将以下任意一项捕获到捕获组1中
  • [^，\ v] + 匹配集合，\ v 中不存在的任何一个或多个字符.该字面上匹配逗号，或垂直空格字符 \ v (例如换行符)
  • (?< =，)匹配上一个标记(使用正向后引号)为逗号的位置，

  ---

  Explanation

  • ([^,\v]+|(?<=,)) Capture either of the following into capture group 1
    • [^,\v]+ Match one or more of any character not present in the set ,\v. This matches the comma , literally, or vertical whitespace characters \v (such as newline characters)
    • (?<=,) Match the position where the previous token (using positive lookbehind) is a comma ,

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