regex for blank string - python-3.x

Question

I have a string as:
s=
"(2021-06-29T10:53:42.647Z) [Denis]: hi
(2021-06-29T10:54:53.693Z) [Nicholas]: TA FOR SHOWING
(2021-06-29T11:58:29.053Z) [Nicholas]: how are you bane
(2021-06-29T11:58:29.053Z) [Nicholas]:
(2021-06-29T11:58:29.053Z) [Nicholas]: #END_REMOTE#
(2021-06-30T08:07:42.029Z) [Denis]: VAL 01JUL2021
(2021-06-30T08:07:42.029Z) [Denis]: ##ENDED AT 08:07 GMT##"
I want to extract the text from it. Expected output as:
comments=['hi','TA FOR SHOWING','how are you bane',' ','#END_REMOTE#','VAL 01JUL2021','##ENDED AT 08:07 GMT##']
What I have tried is:
comments=re.findall(r']:\s+(.*?)\n',s)
regex works well but I'm not able to get the blank text as ''

Answer 1

You can exclude matching the ] instead in the capture group, and if you also want to match the value on the last line, you can assert the end of the string $ instead of matching a mandatory newline with \n
Note that \s can match a newline and also the negated character class [^]]* can match a newline
]:\s+([^]]*)$
Regex demo | Python demo
import re
regex = r"]:\s+([^]]*)$"
s = ("(2021-06-29T10:53:42.647Z) [Denis]: hi\n"
"(2021-06-29T10:54:53.693Z) [Nicholas]: TA FOR SHOWING\n"
"(2021-06-29T11:58:29.053Z) [Nicholas]: how are you bane \n"
"(2021-06-29T11:58:29.053Z) [Nicholas]: \n"
"(2021-06-29T11:58:29.053Z) [Nicholas]: #END_REMOTE#\n"
"(2021-06-30T08:07:42.029Z) [Denis]: VAL 01JUL2021\n"
"(2021-06-30T08:07:42.029Z) [Denis]: ##ENDED AT 08:07 GMT##")
print(re.findall(regex, s, re.MULTILINE))
Output
['hi', 'TA FOR SHOWING', 'how are you bane ', '', '#END_REMOTE#', 'VAL 01JUL2021', '##ENDED AT 08:07 GMT##']
If you don't want to cross lines:
]:[^\S\n]+([^]\n]*)$
Regex demo

Answer 2

You could identify all after the colon into an array from capture group 1.
re.findall(r'(?m):[ \t]+(.*?)[ \t]*$',s)
then loop the array assigning a space to all empty elements.
>>> import re
>>>
>>> s= """
... (2021-06-29T10:53:42.647Z) [Denis]: hi
... (2021-06-29T10:54:53.693Z) [Nicholas]: TA FOR SHOWING
... (2021-06-29T11:58:29.053Z) [Nicholas]: how are you bane
... (2021-06-29T11:58:29.053Z) [Nicholas]:
... (2021-06-29T11:58:29.053Z) [Nicholas]: #END_REMOTE#
... (2021-06-30T08:07:42.029Z) [Denis]: VAL 01JUL2021
... (2021-06-30T08:07:42.029Z) [Denis]: ##ENDED AT 08:07 GMT##
... """
>>>
>>> talk = [re.sub('^$', ' ', w) for w in re.findall(r'(?m):[ \t]+(.*?)[ \t]*$',s)]
>>> print(talk)
['hi', 'TA FOR SHOWING', 'how are you bane', ' ', '#END_REMOTE#', 'VAL 01JUL2021', '##ENDED AT 08:07 GMT##']

Answer 3

Is this what you want?
comments = re.findall(r']:\s(.*?)\n',s)
If the space after : is always one space, \s+ should be \s. \s+ means one or more spaces.

Answer 4

With your shown samples please try following regex.
^\(\d{4}-\d{2}-\d{2}T(?:\d{2}:){2}\d{2}\.\d{3}Z\)\s+\[[^]]*\]:\s+([^)]*)$
Online demo for above regex
Explanation: Adding detailed explanation for above.
^\(\d{4}-\d{2}-\d{2} ##Matching from starting of line ( followed by 4 digits-2 digits- 2 digits here.
T(?:\d{2}:){2} ##Matching T followed by a non-capturing group which is matching 2 digits followed by colon 2 times.
\d{2}\.\d{3}Z\)\s+ ##Matching 2 digits followed by dot followed by 3 digits Z and ) followed by space(s).
\[[^]]*\]:\s+ ##Matching literal [ till first occurrence of ] followed by ] colon and space(s).
([^)]*)$ ##Creating 1st capturing group which has everything till next occurrence of `)`.
With Python3x:
import re
regex = r"^\(\d{4}-\d{2}-\d{2}T(?:\d{2}:){2}\d{2}\.\d{3}Z\)\s+\[[^]]*\]:\s+([^)]*)$"
varVal = ("(2021-06-29T10:53:42.647Z) [Denis]: hi\n"
"(2021-06-29T10:54:53.693Z) [Nicholas]: TA FOR SHOWING\n"
"(2021-06-29T11:58:29.053Z) [Nicholas]: how are you bane \n"
"(2021-06-29T11:58:29.053Z) [Nicholas]: \n"
"(2021-06-29T11:58:29.053Z) [Nicholas]: #END_REMOTE#\n"
"(2021-06-30T08:07:42.029Z) [Denis]: VAL 01JUL2021\n"
"(2021-06-30T08:07:42.029Z) [Denis]: ##ENDED AT 08:07 GMT##")
print(re.findall(regex, varVal, re.MULTILINE))
Output will be as follows with samples shown by OP:
['hi', 'TA FOR SHOWING', 'how are you bane ', '', '#END_REMOTE#', 'VAL 01JUL2021', '##ENDED AT 08:07 GMT##']