Question

我正在开发一个应用程序，其中变量初始化为默认值。

用户可以随时更改这些值。用户应该可以随时将部分或全部变量重置为默认值。

最好的解决方法是什么？

这将是一个解决方案，但我觉得它不是最理想的。你能告诉我我的感觉是否正确以及如何做得更好？

A_DEFAULT = "A_def"
B_DEFAULT = "B_def"
C_DEFAULT = "C_def"

class BusinessLogic_1(object):
    def __init__(self):
        self.setVariablesToDefault()
    def setVariablesToDefault(self, variableNames=None):
        # pass None to set all Variables to default
        variableNames = variableNames or ["A","B","C"]
        if "A" in variableNames:
            self.A = A_DEFAULT
        if "B" in variableNames:
            self.B = B_DEFAULT
        if "C" in variableNames:
            self.C = C_DEFAULT
    def printVariables(self):
        print  "A: %s, B: %s, C: %s" % (self.A, self.B, self.C)

if __name__ == "__main__":
    print "0: Initialize"
    businessLogic_1 = BusinessLogic_1()
    businessLogic_1.printVariables()

    print "Change A,B,C and then reset A,C"
    businessLogic_1.A = "A_new"
    businessLogic_1.B = "B_new"
    businessLogic_1.C = "C_new"
    businessLogic_1.printVariables()

Answer 1

这可能是一个解决方案。这是一种将变量名称作为字符串传递然后通过这些名称访问它们的方法。对象可以同时具有多个名称，但名称始终指向单个对象（在给定的时间点）。

class classWithVariablesThatHaveDefaultValues(object):

    def __init__(self, some, example, variables, defaultValuesDict):
        self.some = some
        self.example = example
        self.variables = variables
        self.dictionaryWithDefaultValues = defaultValuesDict

    def resetValues(self, *listOfVariables):
        for variable in listOfVariables:
            for key in self.dictionaryWithDefaultValues:
                if key == variable:            
                    vars(self)[key] = self.dictionaryWithDefaultValues[key]

if __name__ == "__main__":

    defaultValuesDict = {"some":4, "example":5, "variables":6}
    exampleObject = classWithVariablesThatHaveDefaultValues(1, 2, 3, defaultValuesDict)
    exampleObject.some = 15
    print exampleObject.some, exampleObject.example, exampleObject.variables
    exampleObject.resetValues("example", "some")
    print exampleObject.some, exampleObject.example, exampleObject.variables

输出是：

15 2 3

4 5 3

Answer 2

您可以通过与decimal.localcontext()的工作方式非常相似的方式实现它，但根据您的使用情况，这可能不合适。这将允许您操作并调用反映更新值的原始对象上的任何方法，并在with块的末尾，将它们重置为输入时的值。

from contextlib import contextmanager

class A(object):
    def __init__(self):
        self.a = 3
        self.b = 5
    def display(self):
        return self.a, self.b

a = A()

@contextmanager
def mycontext(obj):
    old_a = obj.a
    old_b = obj.b
    yield obj
    obj.a = old_a
    obj.b = old_b


print 'before:', a.display()
with mycontext(a) as obj:
    print 'entered:', a.display()
    a.a = 3
    a.b = 7
    print 'changed:', a.display()


print 'hopefully original', a.display()

before: (3, 5)
entered: (3, 5)
changed: (3, 7)
hopefully original (3, 5)

如何在Python中将变量重置为标准值

2 个答案: