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Progress Bar
############
When executing longer-running commands, it may be helpful to show progress information,
which updates as your command runs:
.. image:: progress_2.gif
To display progress details, use the ``progress_bar()`` method (which returns a ``ProgressBar`` instance),
pass it a total number of units, and advance the progress as the command executes:
.. code-block:: python
def handle(self):
# Create a new progress bar (50 units)
progress = self.progress_bar(50)
# Start and displays the progress bar
for _ in range(50):
# ... do some work
# Advance the progress bar 1 unit
progress.advance()
# You can also advance the progress bar by more than 1 unit
# progress.advance(3)
# Ensure that the progress bar is at 100%
progress.finish()
Instead of advancing the bar by a number of steps (with the ``advance()`` method),
you can also set the current progress by calling the ``set_progress()`` method.
.. tip::
If your platform doesn't support ANSI codes, updates to the progress bar are added as new lines.
To prevent the output from being flooded, adjust the ``set_redraw_frequency()`` accordingly.
By default, when using a ``max``, the redraw frequency is set to *10%* of your ``max``.
If you don't know the number of steps in advance,
just omit the steps argument when using the ``progress_bar`` method:
.. code-block:: python
progress = self.progress_bar()
The progress will then be displayed as a throbber:
.. code-block:: text
# no max steps (displays it like a throbber)
0 [>---------------------------]
5 [----->----------------------]
5 [============================]
# max steps defined
0/3 [>---------------------------] 0%
1/3 [=========>------------------] 33%
3/3 [============================] 100%
Whenever your task is finished, don't forget to call ``finish()``
to ensure that the progress bar display is refreshed with a 100% completion.
.. note::
If you want to output something while the progress bar is running, call ``clear()`` first.
After you're done, call ``display()`` to show the progress bar again.
Customizing the Progress Bar
============================
Built-in Formats
----------------
By default, the information rendered on a progress bar depends
on the current level of verbosity of the ``IO`` instance:
.. code-block:: text
# Verbosity.NORMAL (CLI with no verbosity flag)
0/3 [>---------------------------] 0%
1/3 [=========>------------------] 33%
3/3 [============================] 100%
# Verbosity.VERBOSE (-v)
0/3 [>---------------------------] 0% 1 sec
1/3 [=========>------------------] 33% 1 sec
3/3 [============================] 100% 1 sec
# Verbosity.VERY_VERBOSE (-vv)
0/3 [>---------------------------] 0% 1 sec
1/3 [=========>------------------] 33% 1 sec
3/3 [============================] 100% 1 sec
# Verbosity.DEBUG (-vvv)
0/3 [>---------------------------] 0% 1 sec/1 sec 1.0 MB
1/3 [=========>------------------] 33% 1 sec/1 sec 1.0 MB
3/3 [============================] 100% 1 sec/1 sec 1.0 MB
.. note::
If you call a command with the quiet flag (``-q``), the progress bar won't be displayed.
Instead of relying on the verbosity mode of the current command,
you can also force a format via ``set_format()``:
.. code-block:: python
progress.set_format('verbose')
The built-in formats are the following:
* ``normal``
* ``verbose``
* ``very_verbose``
* ``debug``
If you don't set the number of steps for your progress bar, use the ``_nomax`` variants:
* ``normal_nomax``
* ``verbose_nomax``
* ``very_verbose_nomax``
* ``debug_nomax``
Custom Formats
--------------
Instead of using the built-in formats, you can also set your own:
.. code-block:: python
progress.set_format('%bar%')
This sets the format to only display the progress bar itself:
.. code-block:: text
>---------------------------
=========>------------------
============================
A progress bar format is a string that contains specific placeholders
(a name enclosed with the ``%`` character); the placeholders are replaced based
on the current progress of the bar. Here is a list of the built-in placeholders:
* ``current``: The current step
* ``max``: The maximum number of steps (or 0 if no max is defined)
* ``bar``: The bar itself
* ``percent``: The percentage of completion (not available if no max is defined)
* ``elapsed``: The time elapsed since the start of the progress bar
* ``remaining``: The remaining time to complete the task (not available if no max is defined)
* ``estimated``: The estimated time to complete the task (not available if no max is defined)
* ``memory``: The current memory usage
* ``message``: The current message attached to the progress bar
For instance, here is how you could set the format to be the same as the ``debug`` one:
.. code-block:: python
progress.set_format(' %current%/%max% [%bar%] %percent:3s%% %elapsed:6s%/%estimated:-6s% %memory:6s%')
Notice the ``:6s`` part added to some placeholders?
That's how you can tweak the appearance of the bar (formatting and alignment).
The part after the colon (``:``) is used to set the format of the string.
The ``message`` placeholder is a bit special as you must set the value yourself:
.. code-block:: python
progress.set_message('Task starts')
progress.start()
progress.set_message('Task in progress...')
progress.advance()
# ...
progress.set_message('Task is finished')
progress.finish()
Bar Settings
------------
Amongst the placeholders, ``bar`` is a bit special as all the characters used to display it can be customized:
.. code-block:: python
# the finished part of the bar
progress.set_bar_character('<comment>=</comment>')
# the unfinished part of the bar
progress.set_empty_bar_character(' ')
# the progress character
progress.set_progress_character('|')
# the bar width
progress.set_bar_width(50)
.. warning::
For performance reasons, be careful if you set the total number of steps
to a high number. For example, if you're iterating over a large number of
items, consider setting the redraw frequency to a higher value by calling
``ProgressHelper.set_redraw_frequency()``, so it updates on only some iterations:
.. code-block:: python
progress.start(50000)
# update every 100 iterations
progress.set_redraw_frequency(100)
for _ in range(50000)
# ... do some work
progress.advance()
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