Incorrect number of arguments for function

[calibricious]

Hello everyone,

Let me preface this with: I have about 24 hours experience with Calibre templating language, so forgive me if I am missing something obvious. I have tried to search the forum and the internet, but found nothing.

The problem

I have written a function maketitle which takes in 6 arguments. For almost all books, it works perfectly, but for a few select cases I get the error

EXCEPTION: Incorrect number of arguments for function maketitle

Details

def evaluate(self, formatter, kwargs, mi, locals, title, author, series, series_index, category, pairing):
[...]

• The function takes in 6 arguments: title, author, series, series_index, category, pairing
  • "category" and "pairing" are custom created columns (values only ever contain 1 word with [A-Za-z]*)
• I wrote the function in Python, but am trying to use it for formatting book titles when I send them to my Kobo. So I guess I'm using it in basic template mode (?)

Debugging

Since it is a basic template, I am running it on the field title

{title:maketitle({author},{series},{series_index},{#category},{#pairing})}

I am getting the following error code in some instances:

EXCEPTION: Incorrect number of arguments for function maketitle

I saw a file named after this error on my Kobo, so I decided to create a column with the same exact template, to visualise where it was going wrong.

I have noticed 2 things:

1. It fails on 3 books (out of over 100) in the column
   • What these books have in common is that their author field contains commas (to be precise, exactly 1 comma)
2. It fails on other books on the Kobo
   • I am unsure of how many or which, because every new error overwrites the previously generated file with the error title
   • I am sure these are files OTHER than the aforementioned 3 books, because I noticed it when I tried to send all files except for the ones with errors

I have also tested removing and adding fields, to see how many arguments it was effectively taking in. Removing 1 argument solved the issue for the 3 books.

My conclusion was that, at least for the column in Calibre, the comma in the authors list is being interpreted not literally but as part of the code. Therefore it is separating "authors" into multiple arguments sent into the function.

What I am looking for

1. Fields as literals (escaping)?

My first instinct was that I needed to pass the field names as literals, so they don't get split into multiple arguments.

I've tried the syntax

{title:maketitle(`{author}`,{series},{series_index},{#category},{#pairing})}

Nothing really changed. I also tried escaping everything (except for title). Still the same error

Incorrect number of arguments for function maketitle

2. Alternative way to use my Python functions in templates

I don't know much about Calibre's templating system, so maybe there's an easier way to do this. I'm open to suggestions.

All I want is to have my makefile function do its job, which is to determine the subdirectory where the book will be saved and establish which data goes into the title and which doesn't. I also want this to work for saving books to disk/device.

[chaley]

I strongly recommend you look at the template language manual.

You are breaking a major rule for Single Function Mode:

Do not use subtemplates (`{ … }`) as function arguments. Instead, use Template Program Mode and General Program Mode.

In addition, the Single Function Mode documentation says:

Important: If you have programming experience, please note that the syntax in Single Function Mode is not what you expect. Strings are not quoted and spaces are significant. All arguments are considered to be constants; there are no expressions.

My suspicion is that in your situation using Template Program Mode is easiest. Something like

{title:'maketitle($, $author, $series, $series_index, $#category, $#pairing)'}

[calibricious]

First and foremost, THANK YOU for taking the time to help me.

Originally Posted by chaley

I strongly recommend you look at the template language manual.

You are breaking a major rule for Single Function Mode:

Believe it or not, I DID look at the manual a bunch of times.
The problem is: I didn't really understand that rule, specifically on how I could avoid doing that, until you showed me the alternative.

Originally Posted by chaley

My suspicion is that in your situation using Template Program Mode is easiest. Something like

{title:'maketitle($, $author, $series, $series_index, $#category, $#pairing)'}

Your suggestion has worked like a charm! Once again, thank you so much!



I also must admit that, although I understand there are 3 different modes, I don't fully understand:

1. How to specify which mode I'm using (is it just syntax?)
2. General Programming Mode. Honestly, I just didn't understand the grammar code block in the man page at all
3. What use cases are adequate for Template Program Mode and which ones are for General Programming Mode
4. When I can and can't use which of them (and whether I can mix them)

[chaley]

Originally Posted by calibricious

I also must admit that, although I understand there are 3 different modes, I don't fully understand:

• How to specify which mode I'm using (is it just syntax?)

Yes. TPM is differentiated from SFM by using quotes in specific places (see the manual). GPM templates start with the string "program:". Python templates (PTM) start with the string "python:"

• General Programming Mode. Honestly, I just didn't understand the grammar code block in the man page at all.

It is a fairly standard programming language syntax, with some stuff borrowed from Algol68 to disambiguate block structure. The grammar defines precedence and nesting.

The manual has lots of examples of GPM templates that should help. Look at those and use the calibre Template tester to experiment.

• What use cases are adequate for Template Program Mode and which ones are for General Programming Mode

GPM is best when the work to be done is complex. TPM is best if the work is simple and you need nesting, you want to use conditional text, or the template exists as part of a larger template expression. PTM is used when you need performance or want to use calibre's APIs.

Personally, I always use GPM or PTM to avoid syntax traps and task complexity outgrowing the other modes. Sometimes I use TPM that calls stored templates (Preferences / Advanced / Template functions) for the complex stuff and where I want to reuse the computation.

• When I can and can't use which of them (and whether I can mix them)

You can use any mode where you can use a template. You can't use GPM or python templates in template expressions, e.g.,

{tags} {#some_column:some_function()} {title:'maketitle($, $author, $series, $series_index, $#category, $#pairing)'}

There are many examples of templates in the manual, in MobileRead Template recipies thread, in Templates: various questions not worth their own thread, and under several of the spoilers the Template language changes thread's first post.

[ownedbycats]

@calibricious - just want to mention I love that username

[chaley]

BTW: the grammar is written in Extended Backus–Naur form.

[calibricious]

Originally Posted by chaley

BTW: the grammar is written in Extended Backus–Naur form.

Thank you so much for the answers! I really appreciate all the guidance (and special thanks for mentioning the Algol background + EBNF, it tickled my brain in all the right ways).

Originally Posted by ownedbycats

@calibricious - just want to mention I love that username

Thank you As someone who is also owned by a cat, I must say: right back at ya