AttributeError (object has no attribute '_cpp_object')

1

Hi
After 2 years of working with 2017.2 version, finally I decided to move to the 2019 version. I have a code that used to work fine in the previous version but I am getting AttributeError in 2019 version that seems to appear in the last line while interpolation. Here is the code:

from dolfin import *

#Initial value
first = 150
second = 180

mesh = UnitSquareMesh(10, 10)

Element = FiniteElement("CG", mesh.ufl_cell(), 1)

V = FunctionSpace(mesh, Element)

# Previous solution
class IC(UserExpression):
    def __init__(self, **kwargs):

        self.FIRST = kwargs["FIRST"]
        self.SECOND = kwargs["SECOND"]

    def eval(self, value, x):

        if  x[0] >= 0.02425- DOLFIN_EPS and x[0] <= 0.02575+ DOLFIN_EPS and (x[1] >= 0.015- DOLFIN_EPS ) and (x[1] <= 0.035+ DOLFIN_EPS ):
            value[0] = self.FIRST

        else:
            value[0] = self.SECOND

IC_2 = IC(FIRST = first, SECOND = second,  degree=0)

# Previous solution
Previous_Solution = interpolate(IC_2, V)

This is the error:

Traceback (most recent call last):
  File "/home/Desktop/0TEST/NEW.py", line 31, in <module>
    Previous_Solution = interpolate(IC_2, V)
  File "/usr/lib/python3/dist-packages/dolfin/fem/interpolation.py", line 73, in interpolate
    Pv.interpolate(v)
  File "/usr/lib/python3/dist-packages/dolfin/function/function.py", line 363, in interpolate
    self._cpp_object.interpolate(u._cpp_object)
AttributeError: 'IC' object has no attribute '_cpp_object'

I am not getting error if I remove the last line but I need to do the interpolation.
Thanks in advance for your help.

2

Guess you Need to add initialization to the expression.
super().__init__(**kwargs)

3

Thanks for the reply. However that was not the fix for this issue. It raises another error:

RuntimeError: Invalid keyword argument
Anyways, I figured it out. Here is the solution for those who may encounter the same issue:

from dolfin import *

#Initial value
first = 150
second = 180

mesh = UnitSquareMesh(10, 10)

Element = FiniteElement("CG", mesh.ufl_cell(), 1)

V = FunctionSpace(mesh, Element)

# Previous solution
class IC(UserExpression):
    def __init__(self, **kwargs):

        super().__init__(degree=kwargs["degree"])

        self.FIRST = kwargs["FIRST"]
        self.SECOND = kwargs["SECOND"]

    def eval(self, value, x):

        if  x[0] >= 0.02425- DOLFIN_EPS and x[0] <= 0.02575+ DOLFIN_EPS and (x[1] >= 0.015- DOLFIN_EPS ) and (x[1] <= 0.035+ DOLFIN_EPS ):
            value[0] = self.FIRST

        else:
            value[0] = self.SECOND
            
    def value_shape(self):
        return ()

IC_2 = IC(FIRST = first, SECOND = second,  degree=0)

# Previous solution
Previous_Solution = interpolate(IC_2, V)
4

Thats because you have to remove kwargs from my statement, as you dont declear it in the initializer

5

Hi,

The function cpp is in the submodule dolfin.function.functionspace. However, dirichletbc.py, in the folder fem, invokes the submodule dolfin.function.functionspace.FunctionSpace. Does not this seem a reason why this type of error can be produced?