indicatif custom formatter https://github.com/console-rs/indicatif/issues/610

main.rs

use std::fmt::Write;
use std::thread;
use std::time::Duration;

use indicatif::{ProgressBar, ProgressState, ProgressStyle};
/// Format in either item/s or s/item depending on the value
fn throughput_formatter(state: &ProgressState, w: &mut dyn Write) {
    let ps = state.per_sec();
    if ps > 1.0 {
        write!(w, "{:.1} item/s", ps).unwrap()
    } else if ps == 0.0 {
        write!(w, "..... ").unwrap()
    } else {
        write!(w, "{:.1} s/item", 1.0 / ps).unwrap()
    }
}

fn main() {
    let pb = ProgressBar::new(2000);

    pb.set_style(
        ProgressStyle::with_template("{spinner:.green}: {throughput}")
            .unwrap()
            .with_key("throughput", throughput_formatter),
    );

    for _ in 0..1024 {
        thread::sleep(Duration::from_millis(20));
        pb.inc(1);
    }
    pb.finish();
}