[Python] 'builtin_function_or_method' object cannot be interpreted as an integer when trying...

While trying to develop python packages using rust code, I had some problems that seem to preceed the function invocation in rust. I've tried to implement this simple function:

use polars:relude:ataFrame as PolarsDataFrame;
use pyo3:relude::*;
use pyo3_polars:yDataFrame;

#[pyfunction]
fn test_print(pydf: PyDataFrame) {
let df: PolarsDataFrame = pydf.into();
println!("Inside print!");
println!("Test print from Rust: {}", df.size());
}

#[pymodule]
fn rustpackage(_py: Python, m: &Bound<PyModule>) -> PyResult<()> {
m.add_function(wrap_pyfunction!(test_print, m)?)?;
Ok(())
}


My cargo.toml looks like this:

[package]
name = "rustpackage"
version = "0.1.0"
edition = "2024"

[dependencies]
polars = "0.50.0"
pyo3 = "0.25.1"
pyo3-polars = "0.23.1"


And my pyproject:

[build-system]
requires = ["maturin>=1,<2"]
build-backend = "maturin"

[project]
name = "rustpackage"
requires-python = ">=3.7"
classifiers = [
"Programming Language :: Rust",
"Programming Language :: Python :: Implementation :: CPython",
"Programming Language :: Python :: Implementation :: PyPy",
]
version = "0.1.0"
description = "Example packge"


Then, when running this script:

from rustpackage import test_print

import polars as pl
from polars._utils.construction.dataframe import dataframe_to_pydf

df = pl.DataFrame(
{
"list_a": [["1", "2", "3"], ["5", "5"]],
"list_b": [["1", "2", "3", "8"], ["5", "1", "1"]],
}
)
pydf = dataframe_to_pydf(df)
test_print(pydf)


I get this error message:

Traceback (most recent call last):
File "~/Workspace/test-polars/run.py", line 13, in <module>
test_print(pydf)
TypeError: argument 'pydf': 'builtin_function_or_method' object cannot be interpreted as an integer


I was expecting sucessfull invocation of test_print fn.

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