import random
 
class Foo():
    def __init__(self, id):
        self.id = id
        self.links = []
    def link(self, *args):
        for i in args:
            if self.id in i.links or i.id in self.links: return False
            else:
                i.links.append(self.id)
                self.links.append(i.id)
                return True
 
 
class_a = Foo(id = 20124)
class_b = Foo(id = 63452)
 
class_a.link(class_b)
print(class_a.links) # [63452]
print(class_b.links) # [20124]

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