Question

当我调用此函数

self.myplot = self.plot(x ='X', y ='Y', kind ='scatter')

继承自pandas.DataFrame的类，而不是执行该函数，而是重新实例化该类，从而创建无限的递归实例。

import pandas as pd

class ChildDataFrame(pd.DataFrame):
    myplot = None

    @property
    def _constructor(self):
        return ChildDataFrame


    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        self['X'] = [2,3]
        self['Y'] = [3,4]

        print('Dataframe: \n',self)
        self.myplot = self.plot(x ='X', y ='Y', kind ='scatter')    

a=ChildDataFrame()

我应该如何调用该函数，以及为什么要重新实例化该类？

如果我将plot（）调用移到类之外，它还会多次实例化该类

import pandas as pd

class ChildDataFrame(pd.DataFrame):
    myplot = None

    @property
    def _constructor(self):
        return ChildDataFrame


    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        self['X'] = [2,3]
        self['Y'] = [3,4]

        print('Dataframe: \n',self)

a=ChildDataFrame()
a.plot(x ='X', y ='Y', kind ='scatter')

提供以下输出：

Dataframe:
    X  Y
0  2  3
1  3  4
Dataframe:
    X  Y
0  2  3
1  3  4
Dataframe:
    X  Y
0  2  3
1  3  4

Answer 1

请看下面的描述，希望对您有所帮助，您可以参考this link

class Base(object):
    def method(self):
        print 'original', type(self), self.__class__

class Derived(Base):
    def method(self):
        print 'derived', type(self), self.__class__
        super(type(self), self).method()
        # super(self.__class__, self).method()

class Subclass(Derived):
    def method(self):
        print 'subclass of derived', type(self), self.__class__
        super(Subclass, self).method()

调用Derived（）。method（）时，结果为

derived <class '__main__.Derived'> <class '__main__.Derived'>
original <class '__main__.Derived'> <class '__main__.Derived'>

这里，两个快捷方式均已正确评估。但是，当您调用Subclass（）。method（）时，结果将变为

subclass of derived <class '__main__.Subclass'> <class '__main__.Subclass'>
derived <class '__main__.Subclass'> <class '__main__.Subclass'>
derived <class '__main__.Subclass'> <class '__main__.Subclass'>
derived <class '__main__.Subclass'> <class '__main__.Subclass'>
... skip ...
RuntimeError: maximum recursion depth exceeded while calling a Python object

在该示例中，调用super（Subclass）可以正常工作，并按预期方式调用Derived.method（）。然后我们在Derived.method（）内部调用super（Subclass），这将导致我们回到递归循环的位置。仅当您有其他类继承自使用错误调用的类

时，此问题才可见

调用一个函数重新实例化该类

1 个答案: