Add attribute to an Instance of an existing Class in Python 2

Question

In my data, I am getting two dictionaries at two different parts. I created a Class object to combine the dictionaries into a single object.

In this example, x and y attributes are the Class dictionaries that are being assigned to D_A_x and D_A_y respectively.

How can I add an attribute to a class instance that has already been created?

class Class_Example:
    def __init__(self,x="NaN",y="NaN"):
        self.x = x; self.y = y
    def get_x(self,var): return(self.x[var])
    def get_y(self,var): return(self.y[var])

D_A = {}
D_A_x = {"a":1}
D_A["instance_1"] = Class_Example(x = D_A_x)
#D_A["instance_1"].get_x("a")

D_A_y = {"b":2}
D_A["instance_1"].__init__(y = D_A_y)

print D_A["instance_1"].get_x("a") #Doesn't work because it has been replaced.

I don't have access to D_A_x and D_A_y at the same time create the Class in one go.

I checked out this, but it didn't help in my situation: Adding base class to existing object in python

score 1 · Answer 1 · answered Oct 06 '15 at 01:08

1

Why not simply do: D_A['instance_1'].y = D_A_y?

answered Oct 06 '15 at 01:08

ganduG

615
6
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score 1 · Accepted Answer · answered Oct 06 '15 at 01:09

Yes, its as you have already noticed, when you call __init__() for your Class_Example class , it overwrites the x and y values with the value passed in , and in the second time, since you do not send in anything for x, it uses the default "NaN" string .

You should not call __init__() again, you can simply set the y attribute. Example -

D_A["instance_1"].y = D_A_y

Add attribute to an Instance of an existing Class in Python 2

2 Answers2