Subclassing class returning pandas dataFrame

In my project I am creating a class with pandas DataFrame as core. The values ​​in the dataframe depend on some specification and I initialize it with a letter representing the data I want to work with. I have put all my functions for creating the dataframe inside __init__

, as I understand that these functions are one only and are not needed for them after initialization. Also I don't want to be able to access these functions after my class is used in later code. (I'm not sure if this is the "pythonic" way to do it).

After creating a base class with methods __str__

and plotData (), I would like to apply some filters and build a new class where the extra column is the filter. I would like to do this in __init__

, but keep everything that has already been done. In other words, I don't want to rewrite the integer __init__

, I just want to add a new column to the base frame.

Similarly, I would like to add an additional plot in the plotData () function

There are already quite a few lines in my source code, but the principles are very similar to the code below.

import pandas as pd
import pylab as pl
class myClass(object):
    def __init__(self, frameType = 'All'):
        def method1():
            myFrame = pd.DataFrame({'c1':[1,2,3],'c2':[4,5,6],'c3':[7,8,9]})
            return myFrame
        def method2():
            myFrame = pd.DataFrame({'c1':[.1,.2,.3],'c2':[.4,.5,.6],'c3':[.7,.8,.9]})
            return myFrame
        def makingChiose(self):
            if self.frameType == 'All':
                variable = method1() + method2() 
            elif self.frameType == 'a':
                variable = method1()
            elif self.frameType == 'b':
                variable = method2()
            else:
                variable =  pd.DataFrame({'c1':[0,0,0],'c2':[0,0,0],'c3':[0,0,0]})
            #print 'FROM __init__ : %s' % variable
            return variable           
        self.frameType = frameType      
        self.cObject = makingChiose(self) # object created by the class
    def __str__(self):
        return str(self.cObject)
    def plotData(self):
        self.fig1 = pl.plot(self.cObject['c1'],self.cObject['c2'])
        self.fig2 = pl.plot(self.cObject['c1'],self.cObject['c3'])
        pl.show()

class myClassAv(myClass):
    def addingCol(self):
        print 'CURRENT cObject \n%s' % self.cObject # the object is visible 
        self.cObject['avarage'] = (self.cObject['c1']+self.cObject['c2']+self.cObject['c3'])/3
        print 'THIS WORKS IN GENERAL\n%s' % str((self.cObject['c1']+self.cObject['c2']+self.cObject['c3'])/3) # creating new column works
    def plotData(self):
        # Function to add new plot to already existing plots
        self.fig3 = pl.plot(self.cObject['c1'],self.cObject['avarage'])
if __name__ == '__main__':
    myObject1 = myClass()
    print 'myObject1 =\n%s' % myObject1
    myObject1.plotData()
    myObject2 = myClass('a')
    print 'myObject2 =\n%s' % myObject2
    myObject3 = myClass('b')
    print 'myObject3 =\n%s' % myObject3
    myObject4 = myClass('c')
    print 'myObject4 =\n%s' % myObject4

    myObject5 = myClassAv('a').addingCol()
    print 'myObject5 =\n%s' % myObject5
    myObject5.plotData()

      

        
        
        
      

    

Most of the code works, at least in initialization, but I have an error when I try to create a new dataframe with an additional column. When I add a new one __init__

, I create a completely new initialization and I lose everything that was already done. I created a new function, but I would rather have an extra column after calling the new class rather than a function inside the new class. The result from the code looks like this:

myObject1 =
    c1   c2   c3
0  1.1  4.4  7.7
1  2.2  5.5  8.8
2  3.3  6.6  9.9
myObject2 =
   c1  c2  c3
0   1   4   7
1   2   5   8
2   3   6   9
myObject3 =
    c1   c2   c3
0  0.1  0.4  0.7
1  0.2  0.5  0.8
2  0.3  0.6  0.9
myObject4 =
   c1  c2  c3
0   0   0   0
1   0   0   0
2   0   0   0
CURRENT cObject 
   c1  c2  c3
0   1   4   7
1   2   5   8
2   3   6   9
THIS WORKS IN GENERAL
0    4
1    5
2    6
myObject5 =
None
Traceback (most recent call last):
  File "C:\Users\src\trys.py", line 57, in <module>
    myObject5.plotData()
AttributeError: 'NoneType' object has no attribute 'plotData'

      

        
        
        
      

    

Question: can I partially override a superclass method to have what was previously inside this method with some new functionality? I would like to initialize myClassAv () in a dataframe with four columns instead of three like myClass (), and I would like to have myClassAv (). PlotData () to plot the third line, but keep two from the base class.

I don't know how to interpret the error and why myObject5 is None, but I suspect it is something with inheritance.

Also, if you have any suggestion that I will do things my own way, I would be grateful for hearing them.