Hi Chrono - thank you very much. I understood the problem and you are right. appreciate your help.

Hi Chrono - thanks for the reply. sorry for posting multiple - it was not showing me when i first posted and i re-posted. i will make sure i dont do that.
Below is my calling code to solve the problem:
def equal_to_24(a,b,c,d):
print(f"input is {a},{b},{c},{d}")
if call24(a,b,c,d) is True:
return '24'
else:
return "It's not possible!"

i am printing the input and i see input displayed for all cases until the last step where it throws STDERR. I am showing last 2 cases output along with error at the end. hope this helps.

Test Passed
Log
input is 4,3,1,6
this one can return 6/(1-(3/4)), your answer is: 24
input is 4,3,1,6
Test Passed
Log
input is 1,1,1,1
Test Passed
Log
input is 13,13,13,13
Test Passed
Log

--------20 Random Test--------

input is 21,28,21,53

Test for: a=21,b=28,c=21,d=53 Example solution: "53-(28+(21/21))"
STDERR
Traceback (most recent call last):
File "main.py", line 83, in
A,B,C,D = filter(lambda x: len(x), re.split("[^\d.]+", useran))
ValueError: not enough values to unpack (expected 4, got 1)

I tested just for the last random case alone and i see its working
Log
input is 21,28,21,53
this one can return 53 - (28 + (21 / 21)), your answer is: 24
input is 21,28,21,53
Test Passed

Can you fix this issue. All cases are passed but i see this STDERR while running random test cases.

Traceback (most recent call last):
File "main.py", line 83, in
A,B,C,D = filter(lambda x: len(x), re.split("[^\d.]+", useran))
ValueError: not enough values to unpack (expected 4, got 1)

to the author. can i get some help. i am getting issue with running random test case. all cases are fine but i see this error.

Traceback (most recent call last):
File "main.py", line 83, in
A,B,C,D = filter(lambda x: len(x), re.split("[^\d.]+", useran))
ValueError: not enough values to unpack (expected 4, got 1)

i am getting issue with running random test case. all cases are fine but i see this error

Traceback (most recent call last):
File "main.py", line 83, in
A,B,C,D = filter(lambda x: len(x), re.split("[^\d.]+", useran))
ValueError: not enough values to unpack (expected 4, got 1)

spent a lot of time on this. then realized my mistake . if this helps others -
dont try to add number and reversenumber in the same iteration to the list or set.
and no need to construct full set of size 65.

Thanks Nekai. that helps.

i started as beginner in python. I am at 8 kyu white. how do i know how many points should i make to move to yellow 6 kyu ? and does a problem show how many points it gives if you solve ?