how to pass an expression from PyCall

[randomx207]

Hi @MilesCranmer,

I would also like to ask: what should I do if I want to generate an initial population (i.e., a sympy expression list, or preorder traversal token list, whatever) in Python, and pass it to julia during the pysr population initialization phase? I have looked at #491 and have clone the source code, but I want to know:

1. Is it possible to modify the function function Population to pass expressions from PyCall?
2. If so, how do I build a pysr tree from python's expression objects? I don't know julia well. Can you help me?

for example, what I want to do is like this

    return Population{T,L}(
        [
            PopMember(
                dataset,
                call_python_and_get_a_tree(),       # here
                options;
                parent=-1,
                deterministic=options.deterministic,
            ) for i in 1:population_size
        ],

[MilesCranmer]

This is tricky, I guess the main thing you can do is modify the PopMember constructor. But other than that there isn’t currently an easy way to specify the way new equations are generated in a fresh population. Maybe also look at MilesCranmer/SymbolicRegression.jl#193 for what I want to do.

For constructing trees, take a look at DynamicExpressions.jl which is how the node type is defined.