Crate polars_excel_writer

A crate for serializing Polars dataframes to Excel Xlsx files.

The polars_excel_writer crate provides two interfaces for writing a dataframe to an Excel Xlsx file:

• ExcelWriter a simple Excel serializer that implements the Polars SerWriter trait to write a dataframe to an Excel Xlsx file.
• PolarsXlsxWriter a more configurable Excel serializer that more closely resembles the interface options provided by the Polars Python write_excel() dataframe method.

ExcelWriter uses PolarsXlsxWriter to do the Excel serialization which in turn uses the rust_xlsxwriter crate.

Examples

An example of writing a Polar Rust dataframe to an Excel file using the ExcelWriter and PolarsXlsxWriter interfaces.

use chrono::prelude::*;
use polars::prelude::*;

fn main() {
    // Create a sample dataframe for the example.
    let mut df: DataFrame = df!(
        "String" => &["North", "South", "East", "West"],
        "Integer" => &[1, 2, 3, 4],
        "Float" => &[4.0, 5.0, 6.0, 7.0],
        "Time" => &[
            NaiveTime::from_hms_milli_opt(2, 59, 3, 456).unwrap(),
            NaiveTime::from_hms_milli_opt(2, 59, 3, 456).unwrap(),
            NaiveTime::from_hms_milli_opt(2, 59, 3, 456).unwrap(),
            NaiveTime::from_hms_milli_opt(2, 59, 3, 456).unwrap(),
            ],
        "Date" => &[
            NaiveDate::from_ymd_opt(2022, 1, 1).unwrap(),
            NaiveDate::from_ymd_opt(2022, 1, 2).unwrap(),
            NaiveDate::from_ymd_opt(2022, 1, 3).unwrap(),
            NaiveDate::from_ymd_opt(2022, 1, 4).unwrap(),
            ],
        "Datetime" => &[
            NaiveDate::from_ymd_opt(2022, 1, 1).unwrap().and_hms_opt(1, 0, 0).unwrap(),
            NaiveDate::from_ymd_opt(2022, 1, 2).unwrap().and_hms_opt(2, 0, 0).unwrap(),
            NaiveDate::from_ymd_opt(2022, 1, 3).unwrap().and_hms_opt(3, 0, 0).unwrap(),
            NaiveDate::from_ymd_opt(2022, 1, 4).unwrap().and_hms_opt(4, 0, 0).unwrap(),
        ],
    )
    .unwrap();

    example1(&mut df).unwrap();
    example2(&df).unwrap();
}

// The ExcelWriter interface.
use polars_excel_writer::ExcelWriter;

fn example1(df: &mut DataFrame) -> PolarsResult<()> {
    let mut file = std::fs::File::create("dataframe.xlsx").unwrap();

    ExcelWriter::new(&mut file).finish(df)
}

// The PolarsXlsxWriter interface. For this simple case it is similar to the
// ExcelWriter interface but it has additional options to support more complex
// use cases.
use polars_excel_writer::PolarsXlsxWriter;

fn example2(df: &DataFrame) -> PolarsResult<()> {
    let mut xlsx_writer = PolarsXlsxWriter::new();

    xlsx_writer.write_dataframe(df)?;
    xlsx_writer.save("dataframe2.xlsx")?;

    Ok(())
}

Second output file (same as the first):

Performance

The table below shows the performance of writing a dataframe using Python Polars, Python Pandas and PolarsXlsxWriter.

• Performance data:

  Test Case	Time (s)	Relative (%)
  Polars	6.49	100%
  Pandas	10.92	168%
  polars_excel_writer	1.22	19%
  polars_excel_writer + zlib	1.08	17%

The tested configurations were:

• Polars: The dataframe was created in Python Polars and written using the write_excel() function. See perf_test.py.
• Pandas: The dataframe was created in Polars but converted to Pandas and then written via the Pandas to_excel() function. See also perf_test.py.
• polars_excel_writer: The dataframe was created in Rust Polars and written using the PolarsXlsxWriter interface. See perf_test.rs.
• polars_excel_writer + zlib: Same as the previous test case but uses the zlib feature flag to enable the C zlib library in conjunction with the backend ZipWriter.

Note: The performance was tested for the dataframe writing code only. The code used to create the dataframes was omitted from the test results.

Re-exports

• pub use ExcelWriter;
• pub use PolarsXlsxWriter;

Modules

• write
  A module that exports the ExcelWriter struct which implements the Polars SerWriter trait to serialize a dataframe to an Excel Xlsx file.
• xlsx_writer
  A module that exports the PolarsXlsxWriter struct which provides an Excel Xlsx serializer that works with Polars dataframes and which can also interact with the rust_xlsxwriter writing engine that it wraps.