Looking for how to create a custom column based on a tag

[kaufman]

I would like to create a custom column that works this way:

If a book has a specific tag (in this case "First"), make the column that tag name.
Otherwise, make it the series name if one exists.
Otherwise, make it the string "Uncategorized".

I know how to do all of this except for checking for a specific tag on a book that might have more then one tag.

{:'first_non_empty(field('tag'), field('Series'),'Uncategorized')'}

I need to replace field('tag') with something that will look for the specific tag, but I have no idea what to put in instead.

Any advice or help would be appreciated.

Thanks.

[eschwartz]

http://manual.calibre-ebook.com/temp...-not-found-val

str_in_list(val, separator, string, found_val, not_found_val)

str_in_list(val, separator, string, found_val, not_found_val) – treat val as a list of items separated by separator, comparing the string against each value in the list. If the string matches a value, return found_val, otherwise return not_found_val. If the string contains separators, then it is also treated as a list and each value is checked.

use "," as separator, val will be field('tags') and you want to search for string "First", then return found_val "First". not_found_val should return empty "" which first_non_empty should skip over, I think.

Personally, I think you should use general program mode for this:

program:
	first_non_empty(
		str_in_list(
			field('tags'),
			",",
			"First",
			"First",
			""
		),
		field('series'),
		"Uncategorized"
	)

[kaufman]

Originally Posted by eschwartz

http://manual.calibre-ebook.com/temp...-not-found-val

using str_in_list(val, separator, string, found_val, not_found_val)

use "," as separator, val will be field('tags') and you want to search for string "First", then return found_val "First". not_found_val should return empty "" which first_non_empty should skip over, I think.

Personally, I think you should use general program mode for this:

program:
	first_non_empty(
		str_in_list(
			field('tags'),
			",",
			"First",
			"First",
			""
		),
		field('series'),
		"Uncategorized"
	)

Thanks, this look very helpful. How do I go about using a program mode?

[theducks]

Originally Posted by kaufman

Thanks, this look very helpful. How do I go about using a program mode?

That is it (the words set that)
Just paste it into the rule

[eschwartz]

Originally Posted by kaufman

Thanks, this look very helpful. How do I go about using a program mode?

http://manual.calibre-ebook.com/temp...l-program-mode

the "program:" at the beginning set the interpreter to use general program mode, which is why I included it.

Much more readable this way, isn't it?

[kaufman]

Originally Posted by eschwartz

http://manual.calibre-ebook.com/temp...l-program-mode

the "program:" at the beginning set the interpreter to use general program mode, which is why I included it.

Much more readable this way, isn't it?

Thanks for the info. This worked perfectly. I was thrown off originally because I was reading you post on my phone.

[kaufman]

One more question.

As suggested, I am using this:

str_in_list(
field('tags'),
",",
"First",
"First",
""
),

as part of my column definition. Is there a way to search for the first tag that doesn't match a specific substring. I have a bunch of tags that start with "FiS-", and I would like to get the first tag that isn't one of them. Something like


str_not_in_list(
field('tags'),
",",
"FiS-*",
##Found Tag##,
""
),

Is there some way to do that?

Thanks.

[eschwartz]

Using list_difference() [see here]:

list_difference(list1, list2, separator) – return a list made by removing from list1 any item found in list2, using a case-insensitive compare. The items in list1 and list2 are separated by separator, as are the items in the returned list.

PHP Code:

list_difference(
    field('tags'),
    "comma,separated,list,of,excluded,tags",
    ","
) 


will return a new list, that contains only the items in list1 (tags field) that are not excluded using list2 ("comma,separated,list,of,excluded,tags")

So try this:

PHP Code:

program:

str_in_list(
    list_difference(
        field('tags'),
        "comma,separated,list,of,excluded,tags",
        ","
    ),
    ",",
    "First",
    "First",
    ""
) 


It appears that the "PHP" BBCode is better than the "CODE" BBCode for this CODE.

[kaufman]

Excellent, thanks. One question:

Is there any way to use a regex string in the "comma,separated,list,of,excluded,tags" so that I don't have to enumerate each one. I have about 10 of them, and I add new ones occasionally as well. They all start with "FiS-". I tried "FiS-.*" and that didn't work.

Thanks for all the help.

[eschwartz]

list comparisons do not accept regexes.

Try using

list_re() [see here]:

list_re(src_list, separator, search_re, opt_replace) – Construct a list by first separating src_list into items using the separator character. For each item in the list, check if it matches search_re. If it does, then add it to the list to be returned. If opt_replace is not the empty string, then apply the replacement before adding the item to the returned list.

Using a "^" to match at the start of string (each tag is evaluated as a string in turn) and the negative lookahead (?!matched-regex-to-ignore) we get:

PHP Code:

program:

list_re(
    field('tags'),
    ',',
    '^(?!send to .*)',
    ''
) 


So the whole program will look like:

PHP Code:

program:

str_in_list(
    list_re(
        field('tags'),
        ",",
        "^(?!send to .*)",
        ""
    ),
    ",",
    "First",
    "First",
    ""
) 


list_re() does not accept a list of regexes, so you must use regex (either|or) for multiple regexes.

[chaley]

You could also use list_re to create a sublist of the source, then list difference to see if the source contains any other elements.