// SPDX-License-Identifier: MIT OR Apache-2.0
//
// Copyright 2022-2025, John McNamara, jmcnamara@cpan.org
//! An example of writing a Polar Rust dataframe to an Excel file. This
//! demonstrates setting a value for Null values in the dataframe. The
//! default is to write them as blank cells.
use polars::prelude::*;
use polars_excel_writer::PolarsExcelWriter;
fn main() -> PolarsResult<()> {
// Create a dataframe with Null values (represented as None).
let df = df! [
"Foo" => [None, Some("A"), Some("A"), Some("A")],
"Bar" => [Some("B"), Some("B"), None, Some("B")],
]?;
// Create a new excel writer.
let mut excel_writer = PolarsExcelWriter::new();
// Set an output string value for Null.
excel_writer.set_null_value("Null");
// Write the dataframe to Excel.
excel_writer.write_dataframe(&df)?;
// Save the file to disk.
excel_writer.save("dataframe.xlsx")?;
Ok(())
}