Question

我定义了以下父类：

class Material(object):
    def newMaterial(self,matPhysLaw, stressState,e,nu,alpha,sigY = 0.0,kM = 0.0,mM = 0.0):
        if (matPhysLaw=="elastic"):
            return ElasticMaterial(self,stressState,e,nu,alpha,sigY,kM,mM)

以下儿童班：

class ElasticMaterial(Material):
    def __init__(self,StressState,e,nu,alpha,sigY=0.0,kM=0.0,mM=0.0):
        #Material.__init__(self,StressState,e,nu,alpha,sigY=0.0,kM=0.0,mM=0.0)
        self.StressState = StressState
        if self.StressState=='threed':
            self.lv=6  #lv is length of stress and strain vectors
        else:
            self.lv=4
        self.e = e
        self.nu = nu
        self.alpha = alpha
        self.sigY = sigY
        self.kM = kM
        self.mM = mM

我正在尝试从基类本身创建子类，我正在调用newMaterial()方法，如下所示：

m2 = Material.newMaterial('elastic','threed',10e6,0.2,1e7)

但是，我收到的错误为newMaterial() is missing 1 positional argument: alpha。我想解释为什么我会收到此错误，我该如何纠正？

Answer 1

如果您直接调用Material.newMaterial(...)，则self不受约束，因此您错过了强制性参数。（您正试图通过newMaterial等方式致电self='elastic'。）

删除参数并将其设为@staticmethod：

class Material(object):

    @staticmethod
    def newMaterial(matPhysLaw, stressState, e, nu, alpha, sigY=0.0, kM=0.0, mM=0.0):
        if matPhysLaw == "elastic":
            # But here you don't need the `self` parameter for instantiation
            return ElasticMaterial(stressState, e, nu, alpha, sigY, kM, mM)

如果您需要保留对该类的引用，请使用@classmethod装饰器：

class Material(object):

    @classmethod
    def newMaterial(cls, matPhysLaw, stressState, e, nu, alpha, sigY=0.0, kM=0.0, mM=0.0):
        if (matPhysLaw=="elastic"):
            return ElasticMaterial(stressState, e, nu, alpha, sigY, kM, mM)
    # Do something with `cls`...

类方法缺少一个位置参数

1 个答案: