Crate zzz

source ·
Expand description

💤 MIT licensed Apache 2.0 licensed

The progress bar with sane defaults that doesn’t slow down your loops. Inspired by tqdm.


zzz = "0.3"


  • Seamless integration with iterators and streams
    • If possible, zzz infers the target size from size_hint()
  • Automagically determines and updates a good printing frequency
  • Very low overhead: doesn’t slow down your loop, pretty much no matter how simple the loop body. On Skylake, the average overhead per iteration for a
    • !Sync/add based progress bar is 3 CPU cycles
    • Sync/add_sync based progress bar is ~40 CPU cycles (depends on how many threads are updating the shared state)

Cargo Features

  • streams: Enables support for .progress() on async streams (futures::streams::Stream)

Usage examples

Adding a progress bar to an iterator

use zzz::ProgressBarIterExt as _;

for _ in (0..1000).into_iter().progress() {
    //                         ^^^^^^^^

If size_hint() for the iterator defines an upper bound, it is automatically taken as the target. Otherwise, a progress indicator (“spinner”) is displayed.

Manually creating and advancing a progress bar

use zzz::ProgressBar;

let mut pb = ProgressBar::with_target(1234);
for _ in 0..1234 {

Manually creating a spinner (for unknown target progress indicator)

use zzz::ProgressBar;

let mut pb = ProgressBar::spinner();
for _ in 0..5678 {


  • Mass-import for the main progress bar type as well as the convenience extension traits.


  • Configuration for a progress bar.
  • Progress bar to be rendered on the terminal.
  • Iterator / stream wrapper that automatically updates a progress bar during iteration.


  • Errors that can ocurr while drawing the progress bar.
  • Determines the unit used for printing iteration speed.


  • Extension trait implemented for all iterators, adding methods for conveniently adding a progress bar to an existing iterator.
  • Trait defining how the progress bar is rendered.