Orekit Jpype - Issue with implementing java interfaces

Orekit Python Wrapper usage
1

Hello Everyone,

I have been experimenting with orekit_jpype for a while and have been using the OrekitFixedStepHandler with my numerical propagator. Below is an example code snippet I came across in the Orekit_jpype examples:

import orekit_jpype as orekit
from jpype import JImplements, JOverride

orekit.initVM()

from org.orekit.propagation.sampling import OrekitFixedStepHandler  # noqa

@JImplements(OrekitFixedStepHandler)
class MyStepHandler:
   dates = []

   @JOverride
   def init(self, s0, t, step):
       pass

   @JOverride
   def handleStep(self, currentState):
       self.dates.append(currentState.getDate())

   @JOverride
   def finish(self, s):
       pass


a = MyStepHandler()
b = MyStepHandler()

print(a.dates is b.dates)

When I run this code, True is printed to the console. This implies that every instance of the MyStepHandler class shares the same dates list. However, this is not the behavior I want. I want each instance of the class to hold its own separate dates list.

To achieve this, I tried moving the initialization of the dates list into the init method, as shown below:

@JOverride
def init(self, s0, t, step):
    self.dates = []

But this resulted in the following error:

print(a.dates is b.dates)
^^^^^^^
AttributeError: 'proxy.MyStepHandler' object has no attribute 'dates'

Is this the correct way to implement this? How can I ensure that each instance of the MyStepHandler class has its own separate dates list?

2

Hi there,

You should make dates an attribute of your class yes, but to do so it should be initialized in the __init__ method, which is the constructor for python.
The init method is inherited from Orekit (written in Java) and is not a constructor, simply a function called by the handler.

Cheers,
Romain.