Create custom data type in Python

Question

Hopefully the title isn’t too misleading, I’m not sure the best way to phrase my question.

I’m trying to create a (X, Y) coordinate data type in Python. Is there a way to create a "custom data type" so that I have an object with a value, but also some supporting attributes?

So far I’ve made this simple class:

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y
        self.tuple = (x, y)

Ideally, I’d like to be able to do something like this:

>>> p = Point(4, 5)
>>>
>>> my_x = p.x    # can access the `x` attribute with "dot syntax"
>>>
>>> my_tuple = p  # or can access the tuple value directly
                  # without needing to do `.tuple`, as if the `tuple`
                  # attribute is the "default" attribute for the object

NOTE I’m not trying to simply display the tuple, I know I can do that with the __repr__ method

In a way, I’m trying to create a very simplified numpy.ndarray, because the ndarrays are a datatype that have their own attributes. I tried looking thru the numpy source to see how this is done, but it was way over my head, haha.

Any tips would be appreciated!

Asked By: AwoeDace

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Answer 1

I am not sure what you want to do with the tuple. p will always be an instance of Point. What you intend to do there won’t work.

If you just don’t want to use the dot notation, you could use a namedtuple or a dataclass instead of a class. Then cast their instances to a tuple using tuple() and astuple().

Using a namedtuple and tuple():

from collections import namedtuple

Point = namedtuple("Point", ["x", "y"])

p = Point(4, 5)

x = p.x
y = p.y

xy = p  # xy = tuple(p) not necessary since namedtuple is already a tuple

Note: namedtuple is immutable, i.e. you can’t change x and y.

Using a dataclasses.dataclass and dataclasses.astuple():

from dataclasses import dataclass, astuple

@dataclass
class Point:
    x: int
    y: int
    
p = Point(4, 5)

x = p.x
y = p.y

xy = astuple(p)

Answered By: Thomas

Create custom data type in Python

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