Progress bars

Prompt_toolkit ships with a high level API for displaying progress bars, inspired by tqdm


The API for the prompt_toolkit progress bars is still very new and can possibly change in the future. It is usable and tested, but keep this in mind when upgrading.

Remember that the examples directory of the prompt_toolkit repository ships with many progress bar examples as well.

Simple progress bar

Creating a new progress bar can be done by calling the ProgressBar context manager.

The progress can be displayed for any iterable. This works by wrapping the iterable (like range) with the ProgressBar context manager itself. This way, the progress bar knows when the next item is consumed by the forloop and when progress happens.

from prompt_toolkit.shortcuts import ProgressBar
import time

with ProgressBar() as pb:
    for i in pb(range(800)):

Keep in mind that not all iterables can report their total length. This happens with a typical generator. In that case, you can still pass the total as follows in order to make displaying the progress possible:

def some_iterable():
    yield ...

with ProgressBar() as pb:
    for i in pb(some_iterable, total=1000):

Multiple parallel tasks

A prompt_toolkit ProgressBar can display the progress of multiple tasks running in parallel. Each task can run in a separate thread and the ProgressBar user interface runs in its own thread.

Notice that we set the “daemon” flag for both threads that run the tasks. This is because control-c will stop the progress and quit our application. We don’t want the application to wait for the background threads to finish. Whether you want this depends on the application.

from prompt_toolkit.shortcuts import ProgressBar
import time
import threading

with ProgressBar() as pb:
    # Two parallel tasks.
    def task_1():
        for i in pb(range(100)):

    def task_2():
        for i in pb(range(150)):

    # Start threads.
    t1 = threading.Thread(target=task_1)
    t2 = threading.Thread(target=task_2)
    t1.daemon = True
    t2.daemon = True

    # Wait for the threads to finish. We use a timeout for the join() call,
    # because on Windows, join cannot be interrupted by Control-C or any other
    # signal.
    for t in [t1, t2]:
        while t.is_alive():

Adding a title and label

Each progress bar can have one title, and for each task an individual label. Both the title and the labels can be formatted text.

from prompt_toolkit.shortcuts import ProgressBar
from prompt_toolkit.formatted_text import HTML
import time

title = HTML('Downloading <style bg="yellow" fg="black">4 files...</style>')
label = HTML('<ansired>some file</ansired>: ')

with ProgressBar(title=title) as pb:
    for i in pb(range(800), label=label):

Formatting the progress bar

The visualisation of a ProgressBar can be customized by using a different sequence of formatters. The default formatting looks something like this:

from prompt_toolkit.shortcuts.progress_bar.formatters import *

default_formatting = [
    Text(' '),
    Text(' '),
    Text(' '),
    Text(' '),
    Text('eta [', style='class:time-left'),
    Text(']', style='class:time-left'),
    Text(' '),

That sequence of Formatter can be passed to the formatter argument of ProgressBar. So, we could change this and modify the progress bar to look like an apt-get style progress bar:

from prompt_toolkit.shortcuts import ProgressBar
from prompt_toolkit.styles import Style
from prompt_toolkit.shortcuts.progress_bar import formatters
import time

style = Style.from_dict({
    'label': 'bg:#ffff00 #000000',
    'percentage': 'bg:#ffff00 #000000',
    'current': '#448844',
    'bar': '',

custom_formatters = [
    formatters.Text(': [', style='class:percentage'),
    formatters.Text(']', style='class:percentage'),
    formatters.Text(' '),
    formatters.Bar(sym_a='#', sym_b='#', sym_c='.'),
    formatters.Text('  '),

with ProgressBar(style=style, formatters=custom_formatters) as pb:
    for i in pb(range(1600), label='Installing'):

Adding key bindings and toolbar

Like other prompt_toolkit applications, we can add custom key bindings, by passing a KeyBindings object:

from prompt_toolkit import HTML
from prompt_toolkit.key_binding import KeyBindings
from prompt_toolkit.patch_stdout import patch_stdout
from prompt_toolkit.shortcuts import ProgressBar

import time

bottom_toolbar = HTML(' <b>[f]</b> Print "f" <b>[x]</b> Abort.')

# Create custom key bindings first.
kb = KeyBindings()
cancel = [False]

def _(event):
    print('You pressed `f`.')

def _(event):
    " Send Abort (control-c) signal. "
    cancel[0] = True
    os.kill(os.getpid(), signal.SIGINT)

# Use `patch_stdout`, to make sure that prints go above the
# application.
with patch_stdout():
    with ProgressBar(key_bindings=kb, bottom_toolbar=bottom_toolbar) as pb:
        for i in pb(range(800)):

            # Stop when the cancel flag has been set.
            if cancel[0]:

Notice that we use patch_stdout() to make printing text possible while the progress bar is displayed. This ensures that printing happens above the progress bar.

Further, when “x” is pressed, we set a cancel flag, which stops the progress. It would also be possible to send SIGINT to the mean thread, but that’s not always considered a clean way of cancelling something.

In the example above, we also display a toolbar at the bottom which shows the key bindings.


Read more about key bindings …