[python] option to turn off the output of click.progressbar

When using the console app in Python, using click progressbar makes it nice to visualize the progress when working for a long time.

However, in some cases, when you put a function of the process that originally used progressbar in the server process or batch process, you may want to turn on / off the output of progressbar with an optional argument.

Here are some code patterns that can be used in such cases. => I found a technique to specify / dev / null for file, so that is the first ...

A simple way to use on UNIX

import sys
import click


def something(items, show_progress=False):
    out = sys.stdout if show_progress else open('/dev/null', 'wb')
    with click.progressbar(items, file=out) as bar:
        for item in bar:
            'abcd' * (1024 * 10)


items = list(xrange(10000))
something(items, show_progress=True)
print '--------'
something(items, show_progress=False)

It seems that you can specify the output destination of click.progressbar with the option file, so if you specify a file object to write to / dev / null, nothing will come out. However, if you want to call a function like this something thousands of times, you should close the properly opened file object.

How to solve with Python technique that can be used even in environment without / dev / null

import functools
from contextlib import contextmanager
import click


@contextmanager
def dummy_bar(items, **kwargs):
    yield items


def something(items, show_progress=False):
    f = click.progressbar if show_progress else dummy_bar
    fbar = functools.partial(f, items, show_pos=True, show_eta=True)

    with fbar() as bar:
        for item in bar:
            'abcd' * (1024 * 10)


items = list(xrange(10000))
something(items, show_progress=True)
print '--------'
something(items, show_progress=False)

Commentary

I defined a function called dummy_bar to create a bar that doesn't output anything. Since click.progressbar is called with the with clause, it is assigned to the variable after ʻasusing contextmanager, that is, iterable given as an argument is returned as it is withyield`. ..

The function to be used is switched with the show_progress option, and the arguments are partially applied in functools.partial so that they can be called uniformly without arguments. So, where it was originally with click.progressbar (..., it is simply with fbar ().

Now the bar according to the behavior of the option is assigned by ʻas, and the rest is ok if you use it like click.progressbar` normally.