project.get(): Accept non-list args (strings)

[ferdnyc]

This is another entry in my award-ineligible series, "Don't make programmers write awkward code" (see OpenShot/libopenshot#266). The target today is project.get() in classes.project_data.

Don't make programmers write awkward code

All over the source tree, there are requests for project data like this:

openshot-qt/src/classes/timeline.py

Lines 46 to 52 in eef6933

	# Get some settings from the project
	fps = project.get(["fps"])
	width = project.get(["width"])
	height = project.get(["height"])
	sample_rate = project.get(["sample_rate"])
	channels = project.get(["channels"])
	channel_layout = project.get(["channel_layout"])

Unlike any other lookup method, ProjectDataStore.get() requires that it be passed a list, or it will fail with a warning:

openshot-qt/src/classes/project_data.py

Lines 68 to 71 in eef6933

	# Verify key is valid type
	if not isinstance(key, list):
	log.warning("get() key must be a list. key: {}".format(key))
	return None

But that just makes the calling code awkward. So, with this change, a non-empty, non-list arg is simply promoted to a single-item list by the code, instead of by the coder:

        if not key:
            log.warning("Cannot get empty key.")
            return None
        if not isinstance(key, list):
            key = [key]

That allows project.get("fps"), project.get("width"), etc. to do what's expected, and makes the code easier to write and to read.

[ferdnyc]

The BEST part of this, the great irony of project.get() requiring that its argument be a list? The whole reason that was done was so that sub-objects could be looked up by path, using the list arg. So, project.get(["fps", "num"]), for example. And, that functionality is made limited use of, by things like the filter() methods in the QueryObject classes.

But project.get() is never, never-EVER called that way, not even once, in the actual code. Not even where it COULD be! Even where sub-keys are looked up, the code doesn't query them using a list. Instead?

openshot-qt/src/classes/exporters/edl.py

Lines 49 to 50 in eb3b19c

	fps_num = get_app().project.get(["fps"]).get("num", 24)
	fps_den = get_app().project.get(["fps"]).get("den", 1)

openshot-qt/src/windows/views/timeline_webview.py

Lines 1772 to 1775 in eb3b19c

	# Get FPS from project
	fps = get_app().project.get(["fps"])
	fps_num = float(fps["num"])
	fps_den = float(fps["den"])

If anyone was ever curious how you can tell when your API isn't quite in sync with the needs of its consumers, that's how.

[DylanC]

@ferdnyc - Simple but effective. I like this change.

[ferdnyc]

@DylanC Thanks! I find the whole idea of the "series" pretty entertaining, actually. I can imagine it really taking off, right down to an awareness campaign featuring awkward novelty t-shirt designs. 😉

This code was what initially inspired it, actually. I ended up tackling libopenshot's logging calls first only because the code they forced was so much more awkward and ugly. This is admittedly minor by comparison. We get to type a whole 2 less characters per call, woo.

[DylanC]

@ferdnyc

This is admittedly minor by comparison. We get to type a whole 2 less characters per call, woo.

Any time saving is better than no time saving. 😄