Day10:Read CSV with csv crate - 100DayOfRust

In last article, I wrote how to read CSV file content, split fields from line, etc.

Instead of reading and processing CSV file manually, Rust has a csv crate can help us.

Let's bring back to our examresult.csv:

Alice, 90
Bob, 85
Chris, 92
Delan, 88

The goal is the same: we read the content, get the second column to calculate the total score and average score.

Let's create a project cargo new csvreader

Then add csv crate to the dependencies section:

[dependencies]
csv = "1.1"

Now let's code our main.rs:

fn read_csv() {
    let mut reader = csv::ReaderBuilder::new()
                        .has_headers(false)
                        .from_path("examresult.csv")
                        .expect("Cannot read fild");
    let mut total_score = 0;
    let mut total_count = 0;
    for record in reader.records() {
        total_score += record.unwrap()[1].trim().parse::<i32>().unwrap();
        total_count += 1;
    }   
    println!("Total score: {} Avg score: {}",
             total_score,
             (total_score as f32) / (total_count as f32));
}


fn main() {
    read_csv();
}

First we create a csv reader from the crate ReaderBuilder function and tell reader our CSV file doesn't have a header, such that our reader will not skip the first line.

Then we iterate reader.records(), record is a type of Result, and the unwrap type is csv::string_record::StringRecord, which we can index field by number like array or vector.

Run the code cargo run, we got:

Total score: 355 Avg score: 88.75

Click to see more information about the csv crate.