[Sugar-devel] [PATCH sugar] Example objects support

[Sascha Silbe]

Martin Abente Lahaye <martin.abente.lahaye at gmail.com> writes:

[src/jarabe/journal/volumestoolbar.py]
[_set_up_activities_examples()]
[...]
> +        activities = []
> +        for home_activity in home_model._activities:
> +            if home_activity.is_journal():
> +                continue
> +
> +            activity_name = home_activity.get_activity_name()
> +            if activity_name not in activities:
> +                self._add_activity_example(home_activity)
> +                activities.append(activity_name)

I wonder if using a dictionary for deduplication would be better
here. E.g.:

    activities = dict([(home_activity.get_activity_name(), home_activity)
                       for home_activity in home_model])
    for home_activity in activities.values():
        self._add_activity_examples(home_activity)


Alternatively, you could just iterate over all entries and let
_add_activity_examples() take care of deduplication (as it has to do
anyway), at the risk of making it O(n²).


> +    def _proper_occurrence(self, home_activity):

What's a "proper" occurrence?

> +        if home_activity.is_journal():
> +            return False
> +
> +        home_model = shell.get_model()
> +        act_name = home_activity.get_activity_name()
> +        activities = filter(lambda act: act_name == act.get_activity_name(),
> +                        home_model._activities)
> +
> +        return len(activities) <= 1

I assume this is for deduplication again. The easiest and fastest way
overall (O(1) per iteration [1], O(n) in total) is probably a
ref-counting scheme:

    def __init__(self, ...):
        # ...the usual stuff...

        self._activity_counts = {}
        self._example_buttons = {}
        for home_activity in home_model:
            self._add_activity(home_activity)

    def _add_activity(self, home_activity):
        """Keep track of an active activity session

        Keep track of an active activity session and add the examples
        folder if available and not already shown.
        """
        name = home_activity.get_activity_name()
        old_count = self._activity_counts.get(name, 0)
        self._activity_counts[name] = old_count + 1
        if old_count:
            return

        # ...create button...

        self._example_buttons[name] = example_button

    def _remove_activity(self, home_activity):
        """Stop keeping track of an active activity session

        Remove all internal references to this session. Remove the
        corresponding examples folder if it's the last instance of
        this activity.
        """
        name = home_activity.get_activity_name()
        old_count = self._activity_counts[name]
        self._activity_counts[name] = old_count - 1
        if old_count > 1:
            return

        example_button = self._example_buttons.pop(name)

        # ...remove button...



> +    def _add_activity_example(self, home_activity):
> +        examples_path = os.path.join(home_activity.get_bundle_path(),
> +                                    'examples')
> +
> +        if not os.path.exists(examples_path):
> +            return

If you add a guard against home_activity.get_bundle_path() returning
None, you can drop the special-casing for the Journal activity.


Sascha

[1] http://wiki.python.org/moin/TimeComplexity#dict
-- 
http://sascha.silbe.org/
http://www.infra-silbe.de/
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