Question

I am adding up the elements from all of the nested lists, so far what I have is

for i in range(len(b)) :
    for j in range(len(b[i])):
        total = total + b[i][j]

But this will not work when an integer value exists in the nested list like,

b = [[1,2], [3,4], [5,6], 1]

In this case i am getting an error message that object of type ‘int’ has no len().
what should i do in this case?

Answer 1

try something like this,
use sum() only when the element is an list or tuple, else simple use the number.

>>> b = [[1,2], [3,4], [5,6], 1]
>>> sum(sum(x) if isinstance(x,(list,tuple)) else x for x in b)
22

improving your solution:

total=0
b = [[1,2], [3,4], [5,6], 1]
for i in range(len(b)) :
    if isinstance(b[i],(list,tuple)):
        for j in range(len(b[i])):
            total += b[i][j]
    else:
        total +=b[i]
print total  #prints 22