List Function

Question

Hello guys!
can you explain me this function? i'm so confused with this output where item's list starts with 0 yes but when i put "len" method, output will be confusing coz it mixed with the start of '0' and starts with '1'.

nums = [1, 2, 3, [1, 2, 3, [2,5,[3]]], 4, 5, 6, []]
print(len(nums[3][3]))
print(len(nums[3][3][2]))

#output:
3
1

Answer 1

First let me clarify what len is.

len means length.
print(len([1, 2, 3, 4]))
>> 4

And for your case, that is a nested list.
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( 1 )
print(len(nums[3][3]))
First we have to get first the element list of nums[3][3]

nums[3] = [1,2,3,[2,5,[3]]]

Now let's get the fourth element of nums[3]

nums[3][3] = [2, 5, [3]]

And the length of this list is 3:
First element: 2
Second element: 5
Third element: [3]
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( 2 )

For the second one, we just need to get the third element of our previous list which is nums[3][3].

nums[3][3] = [2, 5, [3] ]

nums[3][3][2] = [3]

The third element or nums[3][3][2] is [3].

Now the length of [3] is 1.

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If my explanation is still unclear, please feel free to ask. Thanks!

Answer 2

Nice! thank you so much for the very clear explanation!
i got it now it search for the final item in the list then measure what its length.thanks!

Answer 3

I think you still need a little correction. It doesn't search anything and the final item is not important.

The numbers in 'nums[3][3]' are indices! They start counting at 0.
So we access nums,
get the element with index 3, which is
[1, 2, 3, [2,5,[3]]],
and of that list again get the element with index 3, which is the list [2,5,[3]].
The length of that list is 3.

In the next example we have a third index. So from the list [2,5,[3]] we get the element with index 2, which is [3], a list with 1 element.

Add more output to get a better understanding:
print(nums[3])
print(nums[3][3])
print(nums[3][3][2])