Embedding simple CSV file and processing in a functional way

include_str! lines filter is_empty map

In an earlier article I described how to embed a simple CSV file in the code.

I got some suggestions to improve the code from Marcus Bosten. So let's see those.

To remind you the idea was to embed a simple CSV file in the code and then read it into a HashMap.

This is how the CSV file looks like:




This is the new code based on the suggestions from Marcus.

A few notes

  • lines method allows us to iterate over the lines of a string.
  • filter method allow use to, well, filter out some of the entries. In this case we wanted to process only the lines that are not empty.
  • map method processes each entry and for each entry returns something. In this case returns a tuple.
  • split_once is also used to makes sure if there are multiple commas in the string we only split on the first one.
  • This code will panic if there is a non-empty line that has no comma in it. We could also use the filter to filter out and disregard those lines.


use std::collections::HashMap;

fn main() {
    let ext_to_languages = get_languages();

    println!("{:?}", ext_to_languages);
    println!("{:?}", ext_to_languages["rs"]);

    assert_eq!(ext_to_languages["rs"], "rust");

fn get_languages() -> HashMap<String, String> {
    let text = include_str!("../data/languages.csv");

        .filter(|line| !line.is_empty())
        .map(|line| {
            let (key, value) = line.split_once(',').expect("no comma? no results");
            (key.to_owned(), value.to_owned())
        }).collect::<HashMap<String, String>>()

Related Pages

Embedding simple CSV file in Rust application


Gabor Szabo (szabgab)

Gabor Szabo, the author of the Rust Maven web site maintains several Open source projects in Rust and while he still feels he has tons of new things to learn about Rust he already offers training courses in Rust and still teaches Python, Perl, git, GitHub, GitLab, CI, and testing.

Gabor Szabo