FR: Output formatting to omit NA

[Hubbitus]

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Description of your issue, suggested solution and other information

You allow formatting file name of output by templating.
And according to doc, quoting:

Each aforementioned sequence when referenced in an output template will be replaced by the actual value corresponding to the sequence name. Note that some of the sequences are not guaranteed to be present since they depend on the metadata obtained by a particular extractor. Such sequences will be replaced with NA.

If I use it like -o '%(playlist)s.%(playlist_index)s %(title)s.%(ext)s' in config and said download single video, not in playlist, I got file named similar to: NA.NA Viktor Gamov on In-Memory Data Grids.mkv
It is wired.

First simple workaround I found is configure also: --exec 'rename "NA.NA " "" NA.NA* || [ $? -eq 4 ] #{}' (and please note {} goes after comment mark because otherwise we got error on rename if we save multiple files for json and description).

It solve only partial of problem. Files named as expected, but when I start download multiple files - all will be re-downloaded from start, without continue!

My suggestion introduce option to embed python code as formatter something like:

-o '${arg['playlist'] + '.' + str(arg['playlist_index']) if arg['playlist'] != 'NA' else ''} %(title)s.%(ext)s'

It is desired and flexible solution, but will require invent wheel for parsing.

Otherwise possible solution just allow provide lambda function to fully create such string in python style of lambda. Idea borrowed from offlineimap configuration offered.

For example:

--output-lambda '(lambda arg: arg['playlist'] + '.' + str(arg['playlist_index']) + ' ' + arg['title'] + ' - ' + arg['title'] if arg['playlist'] != 'NA' else '') ${arg['playlist'] + '.' + str(arg['playlist_index']) if arg['playlist'] != 'NA' else arg['title'] + ' - ' + arg['title']}'

Obviously arg should be dict and contain keys as described in documentation.

[Hubbitus]

Are you interesting in that future? Have it worth to implement it and provide pull request?

[kristofferR]

I'd love this feature implemented too.