Explanation

If a bar redraws less often than your loop runs, changes its output when piped to a file, or selects a different renderer, these guides explain why.

From an update to a line

A progress update usually follows these three steps. Forced updates can bypass the redraw checks, including the updates made when a bar starts and finishes.

1. Record progress

   Keep the current value when your loop advances or you call bar.update(value).

2. Check whether a redraw is due

   An integer threshold skips most of the work in a fast loop. Calls that pass it are checked against timing and visible progress.

3. Format and write the line

   When a redraw is due, build the display from widgets or the fast renderer’s fixed format and write it to the output stream.

Understand the behaviour

Why doesn’t every update redraw?

Follow the integer threshold and timing checks that decide when a value change produces output. See how min_poll_interval, poll_interval and force=True affect the result.

Why does output change between terminals and logs?

Trace terminal detection, colour support and width selection separately. Find which constructor arguments and environment variables control overwriting a line, using colour and sizing the bar.

What work does the fast path skip?

Separate the update gate, the automatically selected FastProgressBar renderer and the optional native iterator. Learn when custom widgets need the full renderer and what the fast extra changes.

What carries over from the original progressbar?

Check the shared import name and bar lifecycle, then find the modern names for deprecated arguments and attributes. See where compatibility ends, including Python version support and newer APIs.