类中的 Python 字典列表未按预期运行 [重复]

Question

我似乎遇到的问题是，当我运行一个多次使用 plusMinusAverage 类的代码（在我的情况下是一个 for 循环）时，该类的新实例会保留对由之前创建的 pmaDicts 列表的引用之前的 plustMinusAverage 创建并添加到它的末尾。

意义 （导致这种情况的代码在下面）

things = []
for i in range(2):
    thing[i] = plusMinusAverage(count3D=2)
    print thing[i]
    print thing[i].values3D 
>>> (plusMinusAverage at 0x00NSTUFF1)
>>> [{"x":(attr.connection at 0x1234),"y":(attr.connection at 0x2345), etc..},
     {"x":(attr.connection at 0x3456),"y":(attr.connection at 0x4567), etc..}]
>>> (plusMinusAverage at 0x00NSTUFF2)
>>> [{"x":(attr.connection at 0x1234),"y":(attr.connection at 0x2345), etc..},
     {"x":(attr.connection at 0x3456),"y":(attr.connection at 0x4567), etc..},
     {"x":(attr.connection at 0x5678),"y":(attr.connection at 0x6789), etc..},
     {"x":(attr.connection at 0x7890),"y":(attr.connection at 0x8901), etc..}]

让我明白的是，它似乎打印出对象，但随后列表似乎指向原始对象，但条目更多。我不明白为什么该列表不是唯一的。

很抱歉在下面大量发布代码，但我认为这个问题有足够的细微差别，试图制作一个更简单的版本可能会引入不适用于我的情况的解决方案，因为我不确定问题出在哪里确切地说，我将包括所有可能出错的相关部分。 ..另外，也许在 Maya 工作的人可以使用它来构建自己的 shaderNode 工具。

class Tracker2(object):
    dag = ""
    obj = ""
    getTime = "current"

    def setPathing(self):
        if self.nodeName == None:
            self.nodeName = cmds.createNode('transform')
            cmds.addAttr(self.nodeName, sn="type", ln="type", dt="string")
            cmds.setAttr(self.nodeName + ".type", type="string", keyable=0)
        sel = om.MSelectionList()
        sel.add(self.nodeName)
        self.obj = om.MObject()
        self.dag = om.MDagPath()
        sel.getDependNode(0, self.obj)
        try:
            sel.getDagPath(0, self.dag)
        except:
            pass

    def __init__(self):
        if not self.dag and not self.obj:
            self.setPathing()

    def fullpath(self):
        if self.dag and self.dag.fullPathName():
            return self.dag.fullPathName()
        return om.MFnDependencyNode(self.obj).name()

class shaderNode(Tracker2):
    def __init__(self):
        self.nodeName = cmds.shadingNode(self.type,au=1)
        Tracker2.__init__(self)

class connection(object):
    def __init__(self, attr, *args):
        self.attr = attr
    def __set__(self, instance, value):
        if isinstance(value,basestring):
            try:
                cmds.connectAttr(value,instance.fullpath()+"."+self.attr,f=1)
            except Exception as inst:
                cmds.warning(inst)
        elif not value:
            temp = cmds.listConnections(instance.fullpath()+"."+self.attr,s=1,d=0)
            if temp:
                cmds.disconnectAttr(instance.fullpath()+"."+self.attr, temp[0])
        else:
            cmds.warning("Set Connection: Source attribute is non-string value | "+value)
    def __get__(self, instance, owner):
        tempIn = cmds.listConnections(instance.fullpath()+"."+self.attr,s=1,d=0)
        tempIn = tempIn if tempIn else []
        tempOut = cmds.listConnections(instance.fullpath()+"."+self.attr,s=0,d=1)
        tempOut = tempOut if tempOut else []
        #returns list of [[incoming] , [outgoing]]
        return [tempIn,tempOut]

在单独的 py 文件中，其中包含连接的类被加载为 attr

class pmaDict(dict):
    def __init__(self,instance,*args,**kwargs):
        self.instance = instance
        dict.__init__(self,*args,**kwargs)
    def __getitem__(self, key):
        thing = dict.__getitem__(self,key)
        if key in self and isinstance(dict.__getitem__(self, key),attr.Attribute):
            return thing.__get__(self.instance,None)
        if key in self and isinstance(dict.__getitem__(self,key),attr.connection):
            return thing.__get__(self.instance,None)
        else:
            return dict.__getitem__(self,key)

    def __setitem__(self, key, value):
        thing = dict.__getitem__(self,key)
        if key in self and isinstance(dict.__getitem__(self,key),attr.Attribute):
            thing.__set__(self.instance,value)
        elif key in self and isinstance(dict.__getitem__(self,key),attr.connection):
            thing.__set__(self.instance, value)
        else:
            dict.__setitem__(self,key,value)

class plusMinusAvg(attr.shaderNode):
    type = "plusMinusAverage"
    values1D = []
    values2D = []
    values3D = []

    def addInput1D(self):
        i = len(self.values1D)
        print self
        cmds.setAttr(self.fullpath() + ".input1D[" + str(i) + "]", 0)
        newInput = pmaDict(self,
                           {"x": attr.Attribute("input1D[" + str(i) + "]", "float"),
                            "x_con": attr.connection("input1D[" + str(i) + "]")})
        self.values1D.append(newInput)

    def addInput2D(self):
        i = len(self.values2D)
        print self
        cmds.setAttr(self.fullpath() + ".input2D[" + str(i) + "]", 0, 0, type="double2")
        newInput = pmaDict(self,
                           {"xy": attr.Attribute("input2D[" + str(i) + "]", "float"),
                            "x": attr.Attribute("input2D[" + str(i) + "].input2Dx", "float"),
                            "y": attr.Attribute("input2D[" + str(i) + "].input2Dy", "float"),
                            "xy_con": attr.connection("input2D[" + str(i) + "]"),
                            "x_con": attr.connection("input2D[" + str(i) + "].input2Dx"),
                            "y_con": attr.connection("input2D[" + str(i) + "].input2Dy")})
        self.values2D.append(newInput)

    def addInput3D(self):
        i = len(self.values3D)
        print self
        cmds.setAttr(self.fullpath()+".input3D["+str(i)+"]",0,0,0, type="double3")
        newInput = pmaDict(self,
                           {"xyz": attr.Attribute("input3D["+str(i)+"]","double3"),
                            "x": attr.Attribute("input3D["+str(i)+"].input3Dx","float"),
                            "y": attr.Attribute("input3D["+str(i)+"].input3Dy","float"),
                            "z": attr.Attribute("input3D["+str(i)+"].input3Dz","float"),
                            "xyz_con": attr.connection("input3D["+str(i)+"]"),
                            "x_con": attr.connection("input3D["+str(i)+"].input3Dx"),
                            "y_con": attr.connection("input3D["+str(i)+"].input3Dy"),
                            "z_con": attr.connection("input3D["+str(i)+"].input3Dz")})
        self.values3D.append(newInput)

    def __init__(self, count1D=0, count2D=0, count3D=0):
        attr.shaderNode.__init__(self)
        for i in range(count1D):
            self.addInput1D()
        for i in range(count2D):
            self.addInput2D()
        for i in range(count3D):
            self.addInput3D()

Answer 1

问题就在这里：

class plusMinusAvg(attr.shaderNode):
    type = "plusMinusAverage"
    values1D = []
    values2D = []
    values3D = []

您正在将列表分配为类属性。你通常习惯于这样的赋值，因为如果你在方法调用中做类似values1d = blah的事情，赋值将隐式地在self上进行。但是，您永远不会进行其他分配：您只需通过 append、__setitem__ 等方法使用类级列表。因此，所有实例都使用在类对象中定义的相同列表。

要修复，请将三个列表分配移动到 __init__ 内：

self.values1D = []
self.values2D = []
self.values3D = []

这将确保每个实例都有自己的列表。对所有可变属性（例如列表和字典）执行此操作作为一般规则，以避免将来出现相同类型的问题。