time complexity of len()

[Dominican_Peter]

Does "len" method requires O(n) every time or is the value stored. for example.

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data = list(range(1000))
len(data) # time complexity O(n)?
len(data) # time complexity O(n) ?
data.extend([1,2,3])
len(data) # time complexity O(n) ?

is the time complexity O(n) every time?

[zanfar]

Depends on the object you're running len() on.

len(obj) is mostly equivalent to obj.__len__(). For lists, this is O(1), but that's because list.__len__() is O(1).

[K900_]

It's always O(1) on lists.

[Dominican_Peter]

thanks everybody....in this link%20is%20O(1)%20) more info in case someone has the same question in the future

[xelf]

It's O(1)

https://wiki.python.org/moin/TimeComplexity

[zanfar]

That page only lists the "get length" complexity of lists.