Regex conditioning

Question

Consider the following:

a;b{c;d;}e{f;}

How can I split this into three groups like so:

Group 1: a;
Group 2: b{c;d;}
Group 3: e{f;}

I'm learning regular expressions and I was wondering if I could include a if-then-else type logic into the expression.

What I have now:

(.*?{.*?})

This creates two groups like so:

Group 1: a;b{c;d;}
Group 2: e{f;}

which is not what I want as a; and b{c;d;} are merged.

Pseudo if-then-else:

1. Select all characters until either a semi-colon or open curly bracket.
2. If semi-colon then stop and complete group.
3. Else if open curly bracket then continue selecting all characters until closing curly bracket.

Thanks.

Answer 1

Use re.findall

>>> re.findall(r'[^;{]+;?(?:{[^}]*})?', 'a;b{c;d;}e{f;}')
['a;', 'b{c;d;}', 'e{f;}']

OR

This one is the more appropriate one.

>>> re.findall(r'[^;{]+;|[^;{]+(?:{[^}]*})?', 'a;b{c;d;}e{f;}')
['a;', 'b{c;d;}', 'e{f;}']

• [^;{]+ negated character class which matches any char but not of ; or { one or more times.

• | OR

• [^;{]+ any char but not of ; or { followed by an

• (?:{[^}]*})? optional curly brace block.

Answer 2

(?<=;)(?![^{]*})|(?<=}(?!$))

You can use this to split with regex module as re does not support split at 0 width assertions.

import regex
x="a;b{c;d;}e{f;}"
print regex.split(r"(?<=;)(?![^{]*})|(?<=}(?!$))",x,flags=regex.VERSION1)

Output:['a;', 'b{c;d;}', 'e{f;}']

See demo.

https://regex101.com/r/tJ2mW5/8#python