Question

I have a String needs to be split by semi-colon. The easiest way to go is [^;]+. By using this, every semi-colon in the string will be used as a delimiter.

However, in our string, there are some “&” that we do not want to include that ; as a delimiter.

For example, a String

abcd;efg;hij&kl;mn

The expected result would be abcd, efg, hij&kl, mn

Can some one help me to solve this problem?

Answer 1

If you want to match everything outside of “real ;s”:

(?:&|[^;])+

would work. Or (?:&\w+;|[^;])+ if more than just & entities are to be expected.

If your regex engine supports split operations, perhaps this regex (matching semicolons only if not preceded by &amp) is also a good idea

(?<!&amp);

To also allow other entities like above, (?<!&\w+); can be used if your regex implementation supports indefinite repetition inside lookbehind assertions. Most don’t, though, .NET being an exception.

In Python:

>>> import re
>>> re.findall("(?:&|[^;])+", "abcd;efg;hij&kl;mn")
['abcd', 'efg', 'hij&kl', 'mn']
>>> re.split("(?<!&amp);", "abcd;efg;hij&amp;kl;mn")
['abcd', 'efg', 'hij&amp;kl', 'mn']