Progress bars — prompt_toolkit 3.0.50 documentation (original) (raw)

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

Warning

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 directoryof 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 theProgressBar context manager.

The progress can be displayed for any iterable. This works by wrapping the iterable (like range) with theProgressBar 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)): time.sleep(.01)

../_images/simple-progress-bar.png

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): time.sleep(.01)

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)): time.sleep(.05)

def task_2():
    for i in pb(range(150)):
        time.sleep(.08)

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

# 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():
        t.join(timeout=.5)

../_images/two-tasks.png

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 ') label = HTML('some file: ')

with ProgressBar(title=title) as pb: for i in pb(range(800), label=label): time.sleep(.01)

../_images/colored-title-and-label.png

Formatting the progress bar

The visualization 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 = [ Label(), Text(' '), Percentage(), Text(' '), Bar(), Text(' '), Progress(), Text(' '), Text('eta [', style='class:time-left'), TimeLeft(), Text(']', style='class:time-left'), Text(' '), ]

That sequence ofFormatter can be passed to the formatter argument ofProgressBar. 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.Label(), formatters.Text(': [', style='class:percentage'), formatters.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'): time.sleep(.01)

../_images/apt-get.png

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 os import time import signal

bottom_toolbar = HTML(' [f] Print "f" [x] Abort.')

Create custom key bindings first.

kb = KeyBindings() cancel = [False]

@kb.add('f') def _(event): print('You pressed f.')

@kb.add('x') 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)): time.sleep(.01)

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

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 main 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.

../_images/custom-key-bindings.png

Read more about key bindings …