Plugboards equaling null

[eschwartz]

I need a plugboard that will clear all the tags from any books which I send/save.

All my tags are meant only for sorting using calibre, and I don't need them clogging up the content.opf and getting reimported by other people which will just confuse them. I prefer a minimalist tag style.

I suspect it will be somewhere in the functions list, but I don't clearly understand most of the template language.

[chaley]

A plugboard cannot set tags to null (empty). I suggest that you set the tags to some innocuous value, such as the word "None".

[eschwartz]

Well, in the meantime, experimentation has yielded me this:

{tags:format_number()}

By passing nothing to format_number(), I I got the formatting to fail, thus passing null to the plugboard. It's totally a hack, but it seems to works, and doesn't seem likely to set fire to my computer, so that seems to be good.

I guess I could do the same with boolean testing for random garbage, or days_between() a non-date.

[Katsunami]

My suggestion would be this:

- Install "Modify EPUB" plugin.
- Create a "Workspace" library.
- Copy the books you want to export for other people to the Workspace library.
- Remove all tags and other stuff you don't want.
- Use "Polish Books" to update metadata, and "Modify EPUB" to strip all non-DC metadata from the OPF. (Maybe you could check both "Update Metadata and "Remove non-DC metadata" in "Modify EPUB", but I have not tried this yet.)

[DoctorOhh]

Originally Posted by eschwartz

By passing nothing to format_number(), I I got the formatting to fail, thus passing null to the plugboard. It's totally a hack, but it seems to works, and doesn't seem likely to set fire to my computer, so that seems to be good.

I'm confused, how does setting anything in the plugboard prevent metadata from being written to the book during the send or save function?

Maybe you aren't talking about the plugboard?

[eschwartz]

Originally Posted by DoctorOhh

I'm confused, how does setting anything in the plugboard prevent metadata from being written to the book during the send or save function?

Maybe you aren't talking about the plugboard?

I assume the same way plugboards CHANGE metadata that gets written to the book.

I just managed to trick the plugboard into writing a blob of nothingness instead of the tags metadata.

Nothingness doesn't actually exist (outside of a few BookWorlds) so it de facto prevents the metadata being written.

[eschwartz]

Originally Posted by Katsunami

My suggestion would be this:

- Install "Modify EPUB" plugin.
- Create a "Workspace" library.
- Copy the books you want to export for other people to the Workspace library.
- Remove all tags and other stuff you don't want.
- Use "Polish Books" to update metadata, and "Modify EPUB" to strip all non-DC metadata from the OPF. (Maybe you could check both "Update Metadata and "Remove non-DC metadata" in "Modify EPUB", but I have not tried this yet.)

That would be an excellent way to do stuff I don't actually need done.

I like my way better, since with a simple plugboard I have made sure calibre removes all tags from all books, but keps them in the database, and I don't have any tags except keywords I use for search/virtual libraries/notes on library maintenance I am doing.

[Katsunami]

So which plugboards are you using?

[eschwartz]

Originally Posted by eschwartz

Well, in the meantime, experimentation has yielded me this:

{tags:format_number()}

By passing nothing to format_number(), I I got the formatting to fail, thus passing null to the plugboard. It's totally a hack, but it seems to works, and doesn't seem likely to set fire to my computer, so that seems to be good.

I guess I could do the same with boolean testing for random garbage, or days_between() a non-date.

This one.

[Katsunami]

Oh, OK; I thought you used that as an experiment and now found a "real" plugboard to do this. I wouldn't be comfortable to trust on a failure to achieve something. Kovid may plug this hole in the plugboard, after which this won't work anymore.

[eschwartz]

http://manual.calibre-ebook.com/temp...-function-mode

format_number(template) – interprets the value as a number and format that number using a python formatting template such as “{0:5.2f}” or “{0:,d}” or “${0:5,.2f}”. The field_name part of the template must be a 0 (zero) (the “{0:” in the above examples). See the template language and python documentation for more examples. Returns the empty string if formatting fails.

I saw a few mentions of that (by format_number(), days_between(), and the boolean operators) and it sounded perfect.
It sounds quite deliberate, how safe do you think it will be?

[Katsunami]

It is safe now, but still I wouldn't use a failure to achieve something. This could always be changed to return something else. It would be better if a function would be created that deliberately and *always* returns and empty string. empty_string() maybe?

[eschwartz]

What about this? Experimenting on a spare custom column...
A very simple custom function (I'm not quite up to the big stuff yet)