Deep-copy expression

Simple Expression copies are shallow, so

from dolfin import *

exp1 = Expression('t + a*a', t=0.0, a=1.0, degree=2)
exp2 = exp1  # only shallow
exp2.t = 3.14
print(exp1.t)

prints 3.14. How to make a deep-copy of an Expression? (Preferably without dragging the degree and such through the entire code base.)

asked Mar 30, 2017 by nschloe FEniCS User (7,120 points)

This question has been asked here .

commented Mar 30, 2017 by jmmal FEniCS User (5,890 points)

See also here. Something like this works:

exp2 = Expression(exp1.cppcode, **exp1.user_parameters, degree=2)

commented Mar 30, 2017 by johannr FEniCS Expert (17,350 points)

This means I'd have to carry around the degree separately, which I'd really like to avoid. Could I perhaps avoid that by using expr.ufl_element()?

commented Mar 30, 2017 by nschloe FEniCS User (7,120 points)

Yes, you should be able to use exp1.ufl_element().degree().

commented Mar 30, 2017 by johannr FEniCS Expert (17,350 points)

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