What the error is telling, is that you can't convert an entire list into an integer. You could get an index from the list and convert that into an integer:
x = ["0", "1", "2"]
y = int(x[0]) #accessing the zeroth element
If you're trying to convert a whole list into an integer, you are going to have to convert the list into a string first:
x = ["0", "1", "2"]
y = ''.join(x) # converting list into string
z = int(y)
If your list elements are not strings, you'll have to convert them to strings before using str.join:
x = [0, 1, 2]
y = ''.join(map(str, x))
z = int(y)
Also, as stated above, make sure that you're not returning a nested list.