Isn’t it because list is linked list, so to get the Len it has to iterate over the whole list whereas to get emptyness it just have to check if there is a 1st element ?
Like in most reasonable languages. Linked lists would be a terrible implementation for a list where grabbing arbitrary indices is explicitly supported.
And even then, many linked list implementations maintain an updated size or length because checking that is a pretty common operation. So even if that is the implementation, it would still be fast because len(list) is a very common operation so they’d definitely optimize it.
I comment because this is how a social network works, and this is how you keep lemmy alive. My comment has generated a dozen of other comments, so he achieved his goal.
There is not a single question that’s already have been answered on internet, so there no point on asking anything on social plateforms except just for the sake of interacting with other peoples.
If the point of Lemmy is just to generate as many comments as possible with everyone just assuming whatever they want about linked articles without reading them I’ll quickly leave again. I’m here for informed discussion, not for a competition in generating engagement
Don’t know how list are implemented in Python. But in the dumb linked list implementation (like C++ std::list), each element has a “next” member that point the the next element. So, to have list length, you have to do (pseudo code, not actual python code):
len = 0
elt = list.fisrt
while exist(elt):
elt = elt.nextlen++
returnlen
Whereas to test if list is empty, you just have to:
Isn’t it because list is linked list, so to get the Len it has to iterate over the whole list whereas to get emptyness it just have to check if there is a 1st element ?
I’ too lazy to read the article BTW.
why comment if you don’t even want to read the article? python lists are not linked lists, they’re contiguous with a smart growth strategy.
Like in most reasonable languages. Linked lists would be a terrible implementation for a list where grabbing arbitrary indices is explicitly supported.
And even then, many linked list implementations maintain an updated
sizeorlengthbecause checking that is a pretty common operation. So even if that is the implementation, it would still be fast becauselen(list)is a very common operation so they’d definitely optimize it.I comment because this is how a social network works, and this is how you keep lemmy alive. My comment has generated a dozen of other comments, so he achieved his goal.
There is not a single question that’s already have been answered on internet, so there no point on asking anything on social plateforms except just for the sake of interacting with other peoples.
Lemmy is not stackoverflow 😉
If the point of Lemmy is just to generate as many comments as possible with everyone just assuming whatever they want about linked articles without reading them I’ll quickly leave again. I’m here for informed discussion, not for a competition in generating engagement
No,
lenis a constant time operation, at least in most cases I believe.Then please be less lazy next time.
So… it has to iterate over the whole empty list is what you’re saying? like once for every of the zero items in the list?
The list is not necessarily empty. If you were sure it was, why check?
Don’t know how list are implemented in Python. But in the dumb linked list implementation (like C++ std::list), each element has a “next” member that point the the next element. So, to have list length, you have to do (pseudo code, not actual python code):
len = 0 elt = list.fisrt while exist(elt): elt = elt.next len++ return lenWhereas to test if list is empty, you just have to:
return exist(list.first)That’s exactly what I was getting at. Getting length of an empty list would not even enter the loop.
Yes. If it’s empty. But in cases where you need to check, it might as well not be.