Regex Expression For a String

Question

I want to split the string in python.

Sample string:

Hi this is ACT I. SCENE 1 and SCENE 2 and this is ACT II. SCENE 1 and SCENE 2 and more

into the following list:

['Hi this is', 'ACT I. SCENE 1', 'and', 'SCENE2', 'and this is', 'ACT II. SCENE 1',
 'and' , 'SCENE 2', 'and more']

Can someone help me build the regex? The one that I have built is:

(ACT [A-Z]+.\sSCENE\s[0-9]+)]?(.*)(SCENE [0-9]+)

But this is not working properly.

Answer 1

If I understand your requirements correctly, you may use the following pattern:

(?:ACT|SCENE).+?\d+|\S.*?(?=\s?(?:ACT|SCENE|$))

Demo.

Breakdown:

(?:                    # Start of a non-capturing group.
    ACT|SCENE          # Matches either 'ACT' or 'SCENE'.
)                      # Close the non-capturing group.
.+?                    # Matches one or more characters (lazy matching).
\d+                    # Matches one or more digits.
|                      # Alternation (OR).
\S                     # Matches a non-whitespace character (to trim spaces).
.*?                    # Matches zero or more characters (lazy matching).
(?=                    # Start of a positive Lookahead (i.e., followed by...).
    \s?                # An optional whitespace character (to trim spaces).
    (?:ACT|SCENE|$)    # Followed by either 'ACT' or 'SCENE' or the end of the string.
)                      # Close the Lookahead.

Python example:

import re

regex = r"(?:ACT|SCENE).+?\d+|\S.*?(?=\s?(?:ACT|SCENE|$))"
test_str = "Hi this is ACT I. SCENE 1 and SCENE 2 and this is ACT II. SCENE 1 and SCENE 2 and more"

list = re.findall(regex, test_str)
print(list)

Output:

['Hi this is', 'ACT I. SCENE 1', 'and', 'SCENE 2', 'and this is', 'ACT II. SCENE 1', 'and', 'SCENE 2', 'and more']

Try it online.

Answer 2

Here is a working script, albeit a bit hackish:

inp = "Hi this is ACT I. SCENE 1 and SCENE 2 and this is ACT II. SCENE 1 and SCENE 2 and more"
parts = re.findall(r'[A-Z]{2,}(?: [A-Z0-9.]+)*|(?![A-Z]{2})\w+(?: (?![A-Z]{2})\w+)*', inp)
print(parts)

This prints:

['Hi this is', 'ACT I. SCENE 1', 'and', 'SCENE 2', 'and this is', 'ACT II. SCENE 1',
 'and', 'SCENE 2', 'and more']

An explanation of the regex logic, which uses an alternation to match one of two cases:

[A-Z]{2,}              match TWO or more capital letters
(?: [A-Z0-9.]+)*       followed by zero or more words, consisting only of
                       capital letters, numbers, or period
|                      OR
(?![A-Z]{2})\w+        match a word which does NOT start with two capital letters
(?: (?![A-Z]{2})\w+)*  then match zero or more similar terms

Answer 3

You can use re.findall:

import re
s = 'Hi this is ACT I. SCENE 1 and SCENE 2 and this is ACT II. SCENE 1 and SCENE 2 and more'
new_s = list(map(str.strip, re.findall('[A-Z\d\s\.]{2,}|^[A-Z]{1}[a-z\s]+|[a-z\s]+', s)))

Output:

['Hi this is', 'ACT I. SCENE 1', 'and', 'SCENE 2', 'and this is', 'ACT II. SCENE 1', 'and', 'SCENE 2', 'and more']