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Why do tuples and lists both need to exist? (lemmy.ml)

submitted 3 years ago* (last edited 3 years ago) by roastpotatothief@lemmy.ml to c/python@lemmy.ml

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The only differences are that tuples are immutable and that lists have extra methods.

Is there ever a strong need for list-type data to be immutable? Evough to justify a whole extra data-type in the language?

Should they release a python 4 with it removed?

The only thing I can think of is as a default function parameter. This function is okay:

def dothings(a=(1,2)):
    print(a)
    a = (a[0], 3)

But this function misbehaves the second time it is called:

def dothings(a=[1,2]):
    print(a)
    a[1] = 3

But IMO the "mutable arguments" thing is another bug to be fixed in a hypothetical python 4. And even in python 3 you just write the function the recommended way, so there is not such a big problem.

def dothings(a=None):
    if a is None:
        a = [1, 2]
    print(a)
    a[1] = 3

The Python devs are clever guys though. There must be some really important reason to maintain both types?

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[–] tmpod 1 points 3 years ago* (last edited 3 years ago)

I do see what you mean. I’m not sure why it’s important to have different datatypes for structure/order and not for other things. You could have different syntaxes for volumes, distances, and coefficients. You don’t need a separate data-type for each type of quantity, but you could. It would make certain types of algorithms more readable.

Those would be units, not actual data collections/structures, like lists, tuples and so on. They are different things. It wouldn't make sense to have a type for each unit, and it would also be unfeasible to do so. Having different core types for order, structrue, relation and math sets is important, however.

print(id(True))

9476448

print(id(1))

9788608

In what sense is True an alias for 1? It’s a boolean not an integer. It really is a different data-type.

You're right, I misremembered it. But, booleans are in fact subclasses of integers.

It would be more reasonable to remove integers and just use floats. Those two are much more similar.

No, it would not be reasonable. Not only are floats a bad replacement for ints, but I'd argue it would go against Python's principle of being simple but highly flexible and easy to understand. As I've stated, having these different primitive types helps a lot when trying to convey intention.

It’s an interesting way of thinking, and has this whole “pythonic” philosophy, experimenting with different ways of thinking.

Yeah. I also have to say that the term "pythonic" is thrown around a lot and it has a very foggy definition. The Zen of Python (import this) is equally as often cited and, while it certainly provides some nice guidelines, it mustn't be taken word by word. In many ways, the Python language doesn't comply with its Zen, in some situations for good, and others for not so good.

Thanks for sharing. As I said these are not the usual explanations I’ve found on the internet. Your explanations are a bit more convincing than those.

You're welcome! I've found this exchange rather fruitful as it hopefully shed some light on the matter and made me have to take a step back and think clearly about my reasoning. It's great to have these kinds of discussions and have your views challenged :3