heres my code

from operator import itemgetter

class Operation(Enum):

    DELETED = 1
    INSERTED = 2

    def __str__(self):
        return str(self.name.lower())

def distances(a, b):
    """Calculate edit
    distance from a to b"""

    len_a = len(a)
    len_b = len(b)

    twod = [[ ("0","none") for j  in range(len_b + 1)] for i in range(len_a + 1)]

    for i in range(1,len_a + 1 ):
        twod[i][0] = (i,"D")

    for j in range(1,len_b + 1 ):
        twod[0][j] = (j,"I")

    for i in range(1,len_a + 1):
        for j in range(1 , len_b + 1):

            # what woud be cost if the twod[i][j] is taken from twod[i-1][j-1]
            if (a[i] == b[j]):
                c = twod[i-1][j-1][0]
                c = twod[i-1][j-1][0] + 1

            # writing a temporary list which could directly give the operation based on the position of min cost
            arr_list = [(twod[i-1][j][0]+1,'D'),(twod[i][j-1][0]+1,'I'),(c,'S')]

            # getting the (cost,operation) into twod[i][j] based on min cost
            twod[i][j] = min(arr_list, key=lambda x:x[0])

    return twod

here is the error

~/similarities/ $ ./score LesMis1.txt LesMis2.txt
Traceback (most recent call last):
  File "./score", line 35, in <module>
  File "./score", line 30, in main
    d = distances(file1, file2)
  File "/home/ubuntu/similarities/helpers.py", line 43, in distances
    twod[i][j] = min(arr_list, key=lambda x:x[0])
TypeError: '<' not supported between instances of 'str' and 'int'

Haven't seen this in a while, as it is not part of the current CS50x 2019.

This particular issue is with ("0","none"), you probably meant (0, None) (None is a special value, describing the absence of something).

Unrelated, you shouldn't use "D" but Operation.DELETED.

And you should if (a[i - 1] == b[j - 1]): (you start the loop with the index at 1, but want to start comparing the string at index 0).

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