Python 返回该类的所有实例的另一个方法返回的值的总和?
您可以使用类变量:Python 返回该类的所有实例的另一个方法返回的值的总和?,python,python-3.x,Python,Python 3.x,您可以使用类变量: class Square(): def __init__(self, side): self.side = side def getArea(self): return side*side def getAreaOfAllInstances(self): {need to write this method} s1 = Square(2) s2 = Square(3) print(s1.getAre
class Square():
def __init__(self, side):
self.side = side
def getArea(self):
return side*side
def getAreaOfAllInstances(self):
{need to write this method}
s1 = Square(2)
s2 = Square(3)
print(s1.getAreaOfAllInstances()) ===> This should print 13 (2*2 + 3*3)
print(s2.getAreaOfAllInstances()) ===> This should print 13 (2*2 + 3*3)`
但这不是一个干净的解决方案。我宁愿创建另一个类来跟踪正方形。像这样:
class Square():
squares = []
def __init__(self, side):
self.side = side
self.squares.append(self)
def getArea(self):
return self.side * self.side
def getAreaOfAllInstances(self):
return sum(s.getArea() for s in self.squares)
s1 = Square(2)
s2 = Square(3)
print(s1.getAreaOfAllInstances()) #===> This should print 13 (2*2 + 3*3)
print(s2.getAreaOfAllInstances()) # ===> This should print 13 (2*2 + 3*3)
当然你可以:
class Square:
def __init__(self, side):
self.side = side
def getArea(self):
return self.side * self.side
class SquareContainer:
def __init__(self):
self.squares = []
def create_square(self, side):
square = Square(side)
self.squares.append(square)
return square
def getAreaOfAllInstances(self):
return sum(s.getArea() for s in self.squares)
sc = SquareContainer()
s1 = sc.create_square(2)
s2 = sc.create_square(3)
print(sc.getAreaOfAllInstances())
但是请注意,这意味着永远不会收集
Square
s,除非您清空Square.\u all\u instances
属性。您可以使用classmethods来实现这一点
class Square():
_all_instances = []
def __init__(self, side):
self.side = side
self._all_instances.append(self)
def getArea(self):
return side*side
@classmethod
def getAreaOfAllInstances(cls):
return sum(inst.getArea() for inst in cls._all_instances)
输出:
class Square(object):
instances_list = [] # Property of the class
def __init__(self, side):
self.trackInstances(self)
self.side = side
def getArea(self):
return self.side**2
@classmethod
def trackInstances(cls, self):
self.instances_list.append(self)
@classmethod
def getAreaOfAllInstances(cls):
areaSum = sum(map(lambda i: i.getArea(), cls.instances_list))
print('square of all instances: {}'.format(areaSum))
s1 = Square(2)
s2 = Square(3)
s2.getAreaOfAllInstances()
请注意,只执行了
s2.getAreaOfAlliances
,它给出了所有实例的区域。您需要自己在某个地方跟踪所有实例,无论是作为辅助数据结构还是作为类的属性。您为什么需要这样做?@AzatIbrakov,只是想知道这是否可行?参考资料:您如何知道您不再需要特定的Square
,并且可以删除它,以便gc能够抓取它?或者可以存储所有(可能无限)实例?
square of all instances: 13