There is an error while converting image using webapp. It returns this error and I was not following along since a long tie so I dont know what is going on in the files. Please anyone review the error.

The way the current code is set up to be is splitting the giving CHAR_SET in the format [a,b,c,d] using a coma will yield a list of string as follow => ['[a','b','c','d]']. Then the code is getting a sub-array using list(CHAR_SET)[1:-1] will yield ['b', 'c']. As you can see a and d are missing from the list.

Solution:
Before splitting the string we should get a sub-string with only comma separating the characters.

CHAR_SET = "[a,b,c,d]"
CHAR_SET = CHAR_SET[1:-1] # this will be "a,b,c,d"

# now we can just split the string
CHAR_SET = CHAR_SET.split(",") # this will be ['a','b','c','d']