On Sat, 28 Jan 2023 at 16:38, Thomas Ligon <[email protected]> wrote:
>
> Should pickle work for Function and Derivative? I found Sympy issue #4297 and
> the answer seems to be no.
> Nevertheless, here is what I have:
> I have a private dictionary containing expressions of symbols, and everything
> works fine.
> Then I created a new private dictionary that includes Function and
> Derivative, and I can't pickle it. Here are some code snippets:
>
> q1S, q2S = symbols('q1, q2')
> q1F = Function('q1')
> ...
> varX = globals()['CuspData']
> fileName = os.path.join(config.pickle_dir, 'CuspData.pckl')
> f = open(fileName, "wb")
> varX = {'q1d0': q1F(tS), 'q1d1': Derivative(q1F(tS), tS)} # test
> #with evaluate(False): pickle.dump(varX, f)
> pickle.dump(varX, f)
> f.close()
> The error is "Can't pickle q1: attribute lookup q1 on __main__ failed"
You need to call the variable the same name as the function:
q1 = Function('q1')
--
Oscar
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