Read CSV remove (trim) whitespaces from around the values

---

• Sometimes we have a CSV file where the data is aligned nicely using spaces to pad the values. (Most likely a manually maintained CSV file).
• We can tell the CSV reader to trim down does whitespaces.

• In this example we also used the alias attribute of serde to map the real titles in the CSV file to the fieldnames of the struct that can use a much more limited set of characters.

examples/csv/csv-trim-all-the-whitespaces/planets.csv

Planet name,  Distance (AU),  Mass
Mercury,      0.4,            0.055
Venus,        0.7,            0.815
Earth,        1,              1
Mars,         1.5,            0.107
Tesla
Ceres,        2.77,           0.00015
Jupiter,      5.2,            318
Saturn,       9.5,            95
Uranus,       19.6,           14
Neptune,      30,             17
Pluto,        39,             0.00218
Charon,       39,             0.000254

examples/csv/csv-trim-all-the-whitespaces/src/main.rs

#[derive(Debug, serde::Deserialize, serde::Serialize)]
struct Planet {
    #[serde(alias = "Planet name")]
    name: String,

    #[serde(alias = "Distance (AU)")]
    distance: String,

    #[serde(alias = "Mass")]
    mass: String,
}

fn main() {
    let filepath = "planets.csv";

    read_and_print_file(filepath);
    println!();

    for result in read_file_return_results(filepath) {
        match result {
            Ok(planet) => println!("{planet:?}"),
            Err(err) => println!("Error parsing csv {err}"),
        }
    }
    println!();

    for planet in read_file_return_planets(filepath) {
        println!("{planet:?}");
    }
}

fn read_and_print_file(filepath: &str) {
    let csv_text = std::fs::read_to_string(filepath).expect("Error reading file");
    let mut rdr = csv::ReaderBuilder::new()
        .has_headers(true)
        .trim(csv::Trim::All)
        .from_reader(csv_text.as_bytes());

    for result in rdr.deserialize::<Planet>() {
        match result {
            Ok(record) => println!("{:?}", record),
            Err(err) => println!("Error parsing csv {err}"),
        }
    }
}

fn read_file_return_results(filepath: &str) -> Vec<Result<Planet, csv::Error>> {
    let csv_text = std::fs::read_to_string(filepath).expect("Error reading file");
    let mut rdr = csv::ReaderBuilder::new()
        .has_headers(true)
        .trim(csv::Trim::All)
        .from_reader(csv_text.as_bytes());

    rdr.deserialize::<Planet>().collect::<Vec<_>>()
}

fn read_file_return_planets(filepath: &str) -> Vec<Planet> {
    let csv_text = std::fs::read_to_string(filepath).expect("Error reading file");
    let mut rdr = csv::ReaderBuilder::new()
        .has_headers(true)
        .trim(csv::Trim::All)
        .from_reader(csv_text.as_bytes());

    rdr.deserialize::<Planet>()
        .filter_map(|entry| entry.ok())
        .collect::<Vec<_>>()
}

examples/csv/csv-trim-all-the-whitespaces/Cargo.toml

[package]
name = "handle-csv"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
csv = "1.2.2"
serde = { version = "1.0.213", features = ["derive"] }

Planet { name: "Mercury", distance: "0.4", mass: "0.055" }
Planet { name: "Venus", distance: "0.7", mass: "0.815" }
Planet { name: "Earth", distance: "1", mass: "1" }
Planet { name: "Mars", distance: "1.5", mass: "0.107" }
Error parsing csv CSV error: record 5 (line: 6, byte: 175): found record with 1 fields, but the previous record has 3 fields
Planet { name: "Ceres", distance: "2.77", mass: "0.00015" }
Planet { name: "Jupiter", distance: "5.2", mass: "318" }
Planet { name: "Saturn", distance: "9.5", mass: "95" }
Planet { name: "Uranus", distance: "19.6", mass: "14" }
Planet { name: "Neptune", distance: "30", mass: "17" }
Planet { name: "Pluto", distance: "39", mass: "0.00218" }
Planet { name: "Charon", distance: "39", mass: "0.000254" }

Planet { name: "Mercury", distance: "0.4", mass: "0.055" }
Planet { name: "Venus", distance: "0.7", mass: "0.815" }
Planet { name: "Earth", distance: "1", mass: "1" }
Planet { name: "Mars", distance: "1.5", mass: "0.107" }
Error parsing csv CSV error: record 5 (line: 6, byte: 175): found record with 1 fields, but the previous record has 3 fields
Planet { name: "Ceres", distance: "2.77", mass: "0.00015" }
Planet { name: "Jupiter", distance: "5.2", mass: "318" }
Planet { name: "Saturn", distance: "9.5", mass: "95" }
Planet { name: "Uranus", distance: "19.6", mass: "14" }
Planet { name: "Neptune", distance: "30", mass: "17" }
Planet { name: "Pluto", distance: "39", mass: "0.00218" }
Planet { name: "Charon", distance: "39", mass: "0.000254" }

Planet { name: "Mercury", distance: "0.4", mass: "0.055" }
Planet { name: "Venus", distance: "0.7", mass: "0.815" }
Planet { name: "Earth", distance: "1", mass: "1" }
Planet { name: "Mars", distance: "1.5", mass: "0.107" }
Planet { name: "Ceres", distance: "2.77", mass: "0.00015" }
Planet { name: "Jupiter", distance: "5.2", mass: "318" }
Planet { name: "Saturn", distance: "9.5", mass: "95" }
Planet { name: "Uranus", distance: "19.6", mass: "14" }
Planet { name: "Neptune", distance: "30", mass: "17" }
Planet { name: "Pluto", distance: "39", mass: "0.00218" }
Planet { name: "Charon", distance: "39", mass: "0.000254" }