please explain the code fragment

Question

print("A*(B+1+j), if j increments from 0\n\nor\n\nA*(B+j), if j increments from 1\n")

def operation(j):
a=ab[j][0]
b=ab[j][1]
result=a*(b+1+j) # j increments from 0
return str(a) + "+" + str(b) + "=" + str(result)

loop=True
i=0
ab=[[2,3],[3,7],[4,5],[5,8],[6,7],[7,8]]
while loop:
print(operation(i))
i+=1
if i==6:
loop=False
I don’t understand next:
def operation(j):
a=ab[ j][0]
b=ab[j][1]
result=a*(b+1+j)
more specifically:
a=ab[ j][0] or b=ab[j][1]

Answer 1

thanks, in first time don’t understand about list within lists

Answer 2

what is it that you do not understand specifically?

Answer 3

help understand this:
a=ab[j][0]
b=ab[j][0]

Answer 4

okay sure.
ab is a nested list, so lists within lists
sort of like an array in other languages

ab[][] means that the first [] is the number of the list within the list and the second [] is the number within that list again
j is simply from the loop to run through all the numbers

so
lst = [[1,2],[3,4]]
lst[0][0] = 1
lst[0][1] = 2
lst[1][0] = 3
lst[1][1] = 4

lst[0][0] means the 0th list (out of the list of lists) and the 0th number from the 0th list

remember that lists are zero-indexed which means the first element in a list is counted as 0 and the second as 1

Answer 5

you are welcome!