Comments on: code-formatting people: I need your help

By: Marius Gedminas

Marius Gedminas — Tue, 16 Dec 2008 20:34:09 +0000

Here's how I would format these:


cat1, cat2, cat3, cat4, cat5 = [self.categories[x] for x in range(1, 6)]

since it fits in 78 columns (duh!). If it didn't, I'd try


cat1, cat2, cat3, cat4, cat5 = [self.categories[x]
                                for x in range(1, 6)]

and


cat1, cat2, cat3, cat4, cat5 = [
        self.categories[x] for x in range(1, 6)]

On to the second example. I find those repeated “1 if condition else None”
expressions annoying; surely a helper can make them readable


def output_bool(self, x):
    return 1 if x else None

I'd name that helper $outputformat_bool for whatever output format you're
producing.

Next, I'd be inclined to put every tuple element on a separate line, if at
least one of them is so large that it doesn't fit on a single line.


def my_send_methods(self, SendMethod, disabled=False):
    return [(x.id,
             x.display_name,
             dict(selected=output_bool(x == self.preferred_send_method),
                  disabled=output_bool(disabled)),
            ) for x in SendMethod.constants.values()]

For the third example, I see your argument, but I think the intimidation factor
of a single expression spanning 9 lines of code is worse than having people
explicitly make sure the expressions are independent:


employees = ([(0, 'None')] +
             [(x.id, x.display_name,
               dict(selected=output_bool(x.id == employee_id)))
              for x in v2org.employees])
locations = [(x.id, x.display_name,
              dict(selected=output_bool(x.id == location_id))
             for x in v2org.locations]
statuses = [(x.id, x.display_name,
             dict(selected=output_bool(x.id == status_id))
            for x in model.ShiftStatus.select()]
return dict(htmlclass="advancedscheduling", v2org=v2org, name=name,
            employees=employees, locations=locations, statuses=statuses)

Although this particular example has enough regularities to want to extract
them into a helper


def item_list(items, selected_id):
    return [(x.id, x.display_name,
             dict(selected=output_bool(x.id == selected_id))
            for x in items]

employees = [(0, 'None')] + item_list(v2org.employees, employee_id)
locations = item_list(v2org.locations, location_id)
statuses = item_list(model.ShiftStatus.select(), status_id)
return dict(htmlclass="advancedscheduling", v2org=v2org, name=name,
            employees=employees, locations=locations, statuses=statuses)

HTH,

By: Matt Wilson

Matt Wilson — Tue, 16 Dec 2008 19:55:15 +0000

Marius, thanks for the feedback!

By: Marius Gedminas

Marius Gedminas — Tue, 16 Dec 2008 15:34:09 +0000

Here's how I would format these:


cat1, cat2, cat3, cat4, cat5 = [self.categories[x] for x in range(1, 6)]

since it fits in 78 columns (duh!). If it didn't, I'd try


cat1, cat2, cat3, cat4, cat5 = [self.categories[x]
                                for x in range(1, 6)]

and


cat1, cat2, cat3, cat4, cat5 = [
        self.categories[x] for x in range(1, 6)]

On to the second example. I find those repeated "1 if condition else None"
expressions annoying; surely a helper can make them readable


def output_bool(self, x):
    return 1 if x else None

I'd name that helper $outputformat_bool for whatever output format you're
producing.

Next, I'd be inclined to put every tuple element on a separate line, if at
least one of them is so large that it doesn't fit on a single line.


def my_send_methods(self, SendMethod, disabled=False):
    return [(x.id,
             x.display_name,
             dict(selected=output_bool(x == self.preferred_send_method),
                  disabled=output_bool(disabled)),
            ) for x in SendMethod.constants.values()]


employees = ([(0, 'None')] +
             [(x.id, x.display_name,
               dict(selected=output_bool(x.id == employee_id)))
              for x in v2org.employees])
locations = [(x.id, x.display_name,
              dict(selected=output_bool(x.id == location_id))
             for x in v2org.locations]
statuses = [(x.id, x.display_name,
             dict(selected=output_bool(x.id == status_id))
            for x in model.ShiftStatus.select()]
return dict(htmlclass="advancedscheduling", v2org=v2org, name=name,
            employees=employees, locations=locations, statuses=statuses)

Although this particular example has enough regularities to want to extract
them into a helper


def item_list(items, selected_id):
    return [(x.id, x.display_name,
             dict(selected=output_bool(x.id == selected_id))
            for x in items]

employees = [(0, 'None')] + item_list(v2org.employees, employee_id)
locations = item_list(v2org.locations, location_id)
statuses = item_list(model.ShiftStatus.select(), status_id)
return dict(htmlclass="advancedscheduling", v2org=v2org, name=name,
            employees=employees, locations=locations, statuses=statuses)

HTH,

By: Matt Wilson

Matt Wilson — Tue, 16 Dec 2008 14:55:15 +0000

Marius, thanks for the feedback!

By: nes

nes — Mon, 15 Dec 2008 21:55:05 +0000

 
The only real gripe I have with the non-standard bool values. If you must have a bool that can’t be used to do arithmetics create some kind of custom Matt bool:

class mbool:
    def __init__(self,expr):
        self.val=bool(expr)
    def __nonzero__(self):
        return self.val
    def __bool__(self):
        return self.val

then you can also extract the repeating part:

def selected_lst(org_entity, select_id):
    return [(x.id, x.display_name, {'selected':mbool(x.id == status_id)})
            for x in org_entity]

Which allows you to say:
return dict(
    htmlclass="advancedscheduling",
    v2org=v2org,
    name=name,
    employees=[(0, 'None')] + selected_lst(v2org.employees,employee_id),
    locations=selected_lst(v2org.locations,location_id),
    statuses=selected_lst(model_ShiftStatus.select(),status_id),
)

By: Matt Wilson

Matt Wilson — Sat, 13 Dec 2008 17:31:04 +0000

Thanks for the writeup. I think maybe you can do preformatted text with the code tag, and then use lots of nbsp's to indent.
def f(a, b, c): return a + b + c

By: Matt Wilson

Matt Wilson — Sat, 13 Dec 2008 17:29:26 +0000

I'm not against OOP, I just learned how to program in an environment without any OOP people around me, so I doesn't come naturally. And I've worked with some bad programmers that were also OOP fans, so I've read a lot of really ugly OOP code.

For example, I dislike having to hop up four or five or more parent classes to find the code that actually does what I want. So maybe in reaction to that, I'm too far on the opposite extreme, where I avoid any anything but low-level data types and literals.

I write these posts in order to get feedback and hopefully improve. Thanks for your comments.

By: simon

simon — Sat, 13 Dec 2008 11:21:41 +0000

Yuck, mangled my whitespace. I can't find any documentation on how to do preformatted text in Disqus comments, so here's my un-mangled version: http://simonwillison.net/static/2008/code-forma...

By: rgzdev

rgzdev — Sat, 13 Dec 2008 10:03:23 +0000

You are not a fan of OOP are you? A functional language like Erlang seems more apropiate for you, Python's parameter passing is not side effect free so your issue #2 doesn't apply much.

Instead of returning tuples and dictionaries you should be returning class instances where the breaking down into separate lines is more natural. I for one can't understand why selected and disabled aren't properties or methods of employee.

This also makes the code more readable for collaborators, experience tells me highly functional programs tend to be terse on documentation. If you are programming in Python is probably because you appreciate readability, so not only do I expect you to use intermediary variables, I even expect you to give them descriptive names so everybody knows what that value you just calculated is.

I understand you have your style and respect it and given that most of your code is written to work like this its probably a bad idea to switch now, so I'll simply encourage you to follow the advises given by Gary and David about proper indentation.

Nice post, cheers.

By: Matt Wilson

Matt Wilson — Fri, 12 Dec 2008 20:37:22 +0000

David,

I flip-flop a lot on using backslashes vs opening a list on one line
and then putting the meat of the assignments on the next line.

Thanks for the tip on conditional expressions. I'll go back and see
if that approach works. I prefer using None rather than False because
I'm never going to misinterpret None as an integer.

Thanks for the feedback.