python - 确保只运行一个类的一个实例

Question

我有一个基础类，我想将其放入一些代码中。我只希望为给定的应用程序实例化或启动一次，尽管它可能会被调用多次。下面代码的问题是 LowClass 一遍又一遍地启动。我只希望它每次测试启动一次..

import logging

class LowClass:

    active = False

    def __init__(self):
        self.log = logging.getLogger()
        self.log.debug("Init %s" % self.__class__.__name__)
        if self.active:
            return
        else:
            self.active = True
        self.log.debug("Now active!")

class A:
    def __init__(self):
        self.log = logging.getLogger()
        self.log.debug("Init %s" % self.__class__.__name__)
        self.lowclass = LowClass()

class B:
    def __init__(self):
        self.log = logging.getLogger()
        self.log.debug("Init %s" % self.__class__.__name__)
        self.lowclass = LowClass()

class C:
    def __init__(self):
        self.log = logging.getLogger()
        self.log.debug("Init %s" % self.__class__.__name__)
        self.a = A()
        self.b = B()


class ATests(unittest.TestCase):
    def setUp(self):
        pass

    def testOne(self):
        a = A()
        b = B()

    def testTwo(self):
        c = C()

感谢您指出我的问题!!

Answer 1

参见 singleton in python .