Regular expression negative lookbehind of non-fixed length

Question

As the document goes:

This is called a negative lookbehind assertion. Similar to positive lookbehind assertions, the contained pattern must only match

Answer 1

Instead of using Negative Lookbehind, you can use Negative Lookahead with balanced braces.

,(?![^{]*\})

For example:

>>> re.findall(r',..(?![^{]*\})', 'a1,a2,a3,a4,{_some_unknown_length,a5,a6,a7}')
[',a2', ',a3', ',a4']