What am I doing if in the return line i put the name of the class before the returned value?-CodePudding

class Point:

    def __init__(self, x, y):
        self.x = x
        self.y = y
        self.coord = (self.x, self.y)

    def __add__(self, other):
        return Point(self.x   other.x, self.y   other.y)

    p1 = Point(3, 5)
    p2 = Point(7, -2)
    print(p1 p2)    # <__main__.Point object at 0x000001A2DAEF3E20>

If i return like this i got this result. (I know this is the memory address)

But if i return like this:

return self.x   other.x, self.y   other.y

Then I got the actual values (10, 3)

And I don't really understand that I am doing when i type there the name of the class

CodePudding user response：

When you type the name of the class, you're invoking the class constructor to construct a new Point object:

Point(self.x   other.x, self.y   other.y)

When you remove the Point() part, you're just constructing a tuple:

self.x   other.x, self.y   other.y

The tuple prints nicely, but it's not a Point; if you try to add it to another tuple you'll get a concatenated tuple:

>>> (3, 5)   (7, -2)
(3, 5, 7, -2)

and if you try to add it to a Point you'll get an error:

>>> (3, 5)   Point(7, -2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can only concatenate tuple (not "Point") to tuple

What you might want to do is add a __str__ and/or __repr__ method to your Point class so that when you print it, you see x and y rather than the memory address:

class Point:

    def __init__(self, x, y):
        self.x = x
        self.y = y
        self.coord = (self.x, self.y)

    def __add__(self, other):
        return Point(self.x   other.x, self.y   other.y)

    def __str__(self):
        return f"Point({self.x}, {self.y})"

Now you can return a Point object and print it in a way that's more useful:

p1 = Point(3, 5)
p2 = Point(7, -2)
print(p1   p2)    # Point(10, 3)

You might also consider using a dataclass, which automatically defines __init__ and __repr__ in ways that are convenient for this type of use case (I'd also make coord a @property so you don't need to worry about updating it every time x and y change):

from dataclasses import dataclass

@dataclass
class Point:
    x: int
    y: int

    @property
    def coord(self):
        return self.x, self.y

    def __add__(self, other):
        return Point(self.x   other.x, self.y   other.y)

p1 = Point(3, 5)
p2 = Point(7, -2)
print(p1   p2)    # Point(x=10, y=3)

CodePudding user response：

I think what you want is this:

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

    def __add__(self, other):
        return Point(self.x   other.x, self.y   other.y)

p1 = Point(3, 5)
p2 = Point(7, -2)
print(p1 p2)

this will return you a Point instance tuple of coord 10, 3