Preferred way to format a dictionary being passed to a function?

Question

How would I format:

self.bot = servo.Robot({
        'waist': servo.Servo(3, 90, .02, 0),
        'shoulder': servo.Servo(4, 130, .03, 15),
        'elbow': servo.Servo(5, 110, .02, 19),
        'wrist': servo.Servo(6, 20, .01, 9),
        'claw': servo.Servo(7, 40, .01, 0)
    }, [5, 15, 25])

In case that was too much of a mouthful, create a variable called self.bot, make it equal to the return value of self.Robot(servo_dict, num_list), which takes a dict and a list as parameters.

I have already looked in PEP8 and this other Stack Overflow question. I would encourage answers to link to style guides...

Spooky - are you related to [thiefmaster](http://stackoverflow.com/users/298479/thiefmaster) ? :P — Jon Clements, Jan 06 '13 at 17:28
@JonClements Probably not, that's just the [octocat](http://octodex.github.com/) — phihag, Jan 10 '13 at 18:06

kindall · Accepted Answer · 2013-01-06T17:46:23.643

Using the dict constructor, you can at least eliminate typing a bunch of quotes:

self.bot = servo.Robot(dict(
        waist = servo.Servo(3, 90, .02, 0),
        shoulder = servo.Servo(4, 130, .03, 15),
        elbow = servo.Servo(5, 110, .02, 19),
        wrist = servo.Servo(6, 20, .01, 9),
        claw = servo.Servo(7, 40, .01, 0)
    ), [5, 15, 25])

Of course, you can also write a helper function like this:

def servos(**kwargs):
    for k, v in kwargs.iteritems():
        kwargs[k] = servo.Servo(*v)
    return kwargs

And then:

self.bot = servo.Robot(servos(
        waist = (3, 90, .02, 0),
        shoulder = (4, 130, .03, 15),
        elbow = (5, 110, .02, 19),
        wrist = (6, 20, .01, 9),
        claw = (7, 40, .01, 0)
    ), [5, 15, 25])

If you will be doing a lot of dicts-of-instances with different types of instances, you can make the helper generic:

def instance_dict(typ, **kwargs):
    for k, v in kwargs.iteritems():
        kwargs[k] = typ(*v)
    return kwargs

# later...
self.bot = servo.Robot(
               instance_dict(servo.Servo,
                   waist = (3, 90, .02, 0),
                   shoulder = (4, 130, .03, 15),
                   elbow = (5, 110, .02, 19),
                   wrist = (6, 20, .01, 9),
                   claw = (7, 40, .01, 0) ),
               [5, 15, 25])

``servos = lambda **kwargs: map(lambda kv: (kv[0], servo.Servo(*kv[1])), kwargs.items()`` (just because we can) — Jonas Schäfer, Jan 06 '13 at 17:24
"Don't use spaces around the = sign when used to indicate a keyword argument or a default parameter value" -- PEP 8. — charmoniumQ, Jan 06 '13 at 22:31
"sometimes the style guide just doesn't apply. When in doubt, use your best judgment" -- PEP 8. :-) — kindall, Jan 07 '13 at 04:59

Preferred way to format a dictionary being passed to a function?

1 Answers1