Length of a single sublist in python

Question

Lets assume i have a list of 3 sublists

a = [[1,1,1],[1,1,1],[1,1,1]]

If I use the command len(a[0:2]) I get the answer 2 (Because there are two elements(sublists) in the list)

But when I do len(a[2]) and want to get the answer 1 (because there is only one element(sublist) in the list) I actually get the length of the third list (which is 3 in this case).

How could I solve this problem?

Answer 1

You have to specify the range you want to look at.

len(a[1:2]) should do the trick.

len(a[x:y]) simply means "the length of a from element x to y (non-inclusive)"

So if you do len(a[2:2]) the output is 0.

Answer 2

You can use:

print(len(a[2:3]))

Or if want it builtin, do a function:

_len=len
def len(l):
    if _len(l)==0:
        return 0
    elif isinstance(l[0],list):
        return _len(l)
    return _len([l])

a=[[1,1,1],[1,1,1],[1,1,1]]
print(len(a[2]))

Both Output:

1

Answer 3

You need to use len(a[2:3]) :

 a = [[1,2,3],[4,5,6],[7,8,9]]

a[2]
>>> [7, 8, 9] 

len(a[2])
>>> 3

a[2:3]
>>> [[7, 8, 9]] 

len(a[2:3])
>>> 1