如何在 Python 中创建有界 int？

Question

我想创建一个从 子类化的类int，但设置它可以是多少数字的下限和上限。

例如，如果下限是2，那么a = MyClass(1)应该引发异常。

我正在苦苦挣扎，因为int它似乎没有__init__功能，所以我不确定如何从中继承，我的尝试给了我错误。

我该怎么做呢？

Answer 1

这是马上的，没有处理很多错误。class boundedInt:&nbsp; &nbsp; def __init__(self, lower, upper):&nbsp; &nbsp; &nbsp; &nbsp; self.x = None&nbsp; &nbsp; &nbsp; &nbsp; if (lower <= upper):&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; self.lower = lower&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; self.upper = upper&nbsp; &nbsp; &nbsp; &nbsp; else:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; raise ValueError("Lower Bound must be lesser than Upper Bound".format())&nbsp;&nbsp;&nbsp; &nbsp; def assign(self, x):&nbsp; &nbsp; &nbsp; &nbsp; if (x>= self.lower and x<=self.upper):&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; self.x = x&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return self.x&nbsp; &nbsp; &nbsp; &nbsp; else:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; raise ValueError("Not in bounds")myInt = boundedInt(15,20) # create object myIntf = myInt.assign(17) # assigns value to a variable

Answer 2

尝试这个。它应该适用于ints 和floats：def BoundedNumber(number_class):&nbsp; &nbsp; def BoundedNumberClassCreator(class_name, lower_bound, upper_bound):&nbsp; &nbsp; &nbsp; &nbsp; if upper_bound and lower_bound and upper_bound < lower_bound:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; raise ValueError(f"Upper bound {upper_bound} is lower than the lower bound {lower_bound}")&nbsp; &nbsp; &nbsp; &nbsp; def new(cls, number):&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if lower_bound and number < lower_bound:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; raise ValueError(f"{number} is below the lower bound of {lower_bound} for this class")&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if upper_bound and upper_bound < number:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; raise ValueError(f"{number} is above the upper bound of {upper_bound} for this class")&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return number_class(number)&nbsp; &nbsp; &nbsp; &nbsp; return type(class_name, (number_class,),&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {"__new__": new,&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;"__doc__": f"Class that acts like `{number_class.__name__}` but has an inclusive lower bound of {lower_bound} and an inclusive upper bound of {upper_bound}",&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;"lower_bound": lower_bound,&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;"upper_bound": upper_bound})&nbsp; &nbsp; return BoundedNumberClassCreatorBoundedInt = BoundedNumber(int)BoundedFloat = BoundedNumber(float)if __name__ == "__main__":&nbsp; &nbsp; IntBetween50And150 = BoundedInt('IntBetween50And150', 50, 150)&nbsp; &nbsp; print(IntBetween50And150(100) == 100)&nbsp; # True&nbsp; &nbsp; try:&nbsp; &nbsp; &nbsp; &nbsp; IntBetween50And150(200)&nbsp; &nbsp; except ValueError as e:&nbsp; &nbsp; &nbsp; &nbsp; print(f"Caught the ValueError: {e}")&nbsp; # Caught the value error: 200 is above the upper bound of 150 for this class&nbsp; &nbsp; print(IntBetween50And150(50.5))&nbsp; # 50&nbsp; &nbsp; print(IntBetween50And150.__doc__) # Class that acts like `int` but has an inclusive lower bound of 50 and an inclusive upper bound of 150子类化的难点int在于它没有__init__函数。相反，您必须使用该__new__功能。该类BoundedNumber负责这一点，定义了一个__new__函数，该函数既通过调用(or ) 运行int(or float)函数，又在执行此操作之前运行自己的边界检查。__new__intfloat由于我们想动态创建一个新类，我们将不得不使用该type函数。这将允许我们在运行时创建一个具有我们想要的任何边界的新类。从技术上讲，要回答您的问题，您只需要在BoundedNumberClassCreator使用int的任何地方加上 with number_class，但由于它也适用于floats，我想我会封装它以减少重复代码。这个解决方案的一件奇怪的事情是如果你ZeroToOne = BoundedInt('ZeroToOne', 0, 1)然后创建i = ZeroToOne(1.1)它会抛出一个错误，即使int(1.1)它在指定的范围内。如果你不喜欢这个功能，你可以new在BoundedNumberClassCreator.