咸菜和象征性表达的评估

Question

I have the problem that pickling/unpickling of sympy expressions may not return the inital expression, as in the following example

>>>with evaluate(False) : x = atan(sqrt(3))
>>>x
atan(sqrt(3))
>>> y = pickle.dumps(x)
>>> z = pickle.loads(y)
>>> z
pi/3

Is there a way to avoid the evaluation in the process?

The motivation is that I need to add sympy expressions to a request.session object in Django without them being altered in the process.

Answer 1

The comment by user2357112 answers the question.

>>>with evaluate(False) : x = atan(sqrt(3))
>>>x
atan(sqrt(3))
>>> y = pickle.dumps(x)
>>> with evaluate(False) : z = pickle.loads(y)
>>> z
atan(sqrt(3))