Do special functions get called every time I create an object?-CodePudding

Just like the __init__() method, do the other special functions get called automatically when I create an object?

Check out this simple class for example:

class Point:
    def __init__(self, x = 0, y = 0):
        self.x = x
        self.y = y
    
    def __str__(self):
        return "({0},{1})".format(self.x,self.y)

Is the __str__() method called automatically when I create a new object?

CodePudding user response：

No. Magic/special methods are only get called when their time arrives. When you create an instance of your class, your initializer method (__init__) is get called. when you print your object, the __str__ method gets called. This is in print() line, not when you create an instance of your class.

Put a simple print statement inside your methods, and run your script in interactive mode to see when which method is gets called.

CodePudding user response：

No, it is only called when you do point.__str__(). Only the __init__ function is called when you create the objext.

CodePudding user response：

At each time you create an object, the __init__ method is called.

At each time you print an object, the __str__ method is called to get.

class Point:
    def __init__(self, x = 0, y = 0):
        print('__init__')
        self.x = x
        self.y = y
    
    def __str__(self):
        print('__str__')
        return "({0},{1})".format(self.x,self.y)

>>> p = Point(3, 2)
__init__

>>> print(p)
__str__
(3,2)

>>> p
<__main__.Point at 0x7fa3ab341940>