TypeError for handle Bool values in deep call chain.

[peacemo]

Environment:

• Windows 11
• Julia 1.7.3 (2022-05-06)
• PyCall v1.94.1

---

Hello, when I use PyCall to pass a Julia function into a Python function, it seems that PyCall does not handle the Bool (true & false) values correctly.

The call chain is seemly like this:

JuliaFunA(JuliaFunB())
  |
  |->Pythonfun(JuliaFunB())

Specifically, I use Python's sklearn.feature_selection.SequentialFeatureSelector to do some feature selection. and in this selector, it gets an argument scoring which is a callable function. So in my Julia code, I use pystring py""" """ to wrap the selector and pass my Julia function into it. Here is my code:

function sequentialfs(mdl, fun, X, y)
    X = Array(X)
    y = Array(y)

    score = fun(mdl, X, y)
    # j = fun(y)

    py"""
    import sklearn.feature_selection as fs
    def test(mdl, fun, X, y):
        score = fun(mdl, X, y)  # situation 1: the fun can run well if been called from here
        return score
        # sfs = fs.SequentialFeatureSelector(
        #     mdl,
        #     n_features_to_select="auto",
        #     direction="forward",
        #     scoring=fun  # situation 2: the fun cannot run if been passed deeper. 
        # )
        # sfs.fit(X, y)
        # return sfs.get_support(indices=true)
    """
    score = py"test"(mdl, fun, X, y)
    return score
end

function custom_score(estimator, X, y_true)
    y_pred = estimator.predict(X)  # Python sklearn predict function
    score = 1 - sum(abs.(y_pred - y_true)) / length(y_true)
    return score
end

iris_X, iris_y = get_some_data()
mdl = function_return_a_sklearn_classifier(iris_X, iris_y)
sequentialfs(mdl, custom_score, iris_X, iris_y)

In situation 1, if the fun (julia -> julia -> Python and run) could be called well, in situation 2, the fun (julia -> julia -> Python -> Python) does not run well, and there is a Python TypeError:

ERROR: PyError ($(Expr(:escape, :(ccall(#= C:\Users\Public\xxxxxx\.julia\dev\PyCall\src\pyfncall.jl:43 =# @pysym(:PyObject_Call), PyPtr, (PyPtr, PyPtr, PyPtr), o, pyargsptr, kw))))) <class 'NameError'>
NameError("name 'true' is not defined")
File "C:\Users\xxxxxx\TongYuan\.julia\dev\PyCall\src\pyeval.jl", line 12, in test
ns = PyDict{String,PyObject}()