Question

是否可以在类函数中使用静态变量（如在C ++中）以下内容并未给出我所期望的内容动机是初始化（非常昂贵的过程）函数内的查找列表 - 但仅限于调用它时对同一函数的后续调用不应该再次初始化变量有没有成语来实现这个目标？
如果函数与类对齐，则很好;因此规则的值可用于'A'的所有实例

>>> class A:
...     def func(self):
...         if not hasattr(self.func,"rules"):
...             print 'initialize'
...             rules=[8,7,6]
...         rules.append(4)
...         return rules
...         
>>> a=A()
>>> for x in range(5):
...     print a.func()
...     

initialize
[8, 7, 6, 4]
initialize
[8, 7, 6, 4]
initialize
[8, 7, 6, 4]
initialize
[8, 7, 6, 4]
initialize
[8, 7, 6, 4]

Answer 1

class A(object): # subclass object for newstyle class
    def func(self, rules=[]):
        if not rules:
            rules[:] = [8, 7, 6]        
        rules.append(4)
        return rules

>>> a = A()
>>> for x in range(5):
        print a.func()


[8, 7, 6, 4]
[8, 7, 6, 4, 4]
[8, 7, 6, 4, 4, 4]
[8, 7, 6, 4, 4, 4, 4]
[8, 7, 6, 4, 4, 4, 4, 4]

Answer 2

如果您希望变量与类关联，请将其存储在类中：

class A(object):
    def func(self):
        if not hasattr(A,"rules"):
            print 'initialize'
            A.rules=[8,7,6]
        A.rules.append(4)
        return rules

在函数中初始化静态成员变量

2 个答案: