[chaley]

Originally Posted by un_pogaz

It's a pity but it's "normal" because you use the function as Calibre calls it itself. It's a point to underline in their doc and usage.

Je comprends la française. For conversations between us feel free to write in French it if you think you will be clearer. I can write in French if needed, but my grammar and vocabulary aren't good. Des faux amis me donne beaucoup de problèmes.

I was just writing a post to say that overnight I found convincing arguments for this ability.

• There are people with a library of stored functions and/or templates. This lets the person use their library, converting to python as and when needed.
• Some of the built-in functions are complicated, for example list_re_group(). No need to bother to rewrite these.
• Some built-in functions would be hard to rewrite, for example template().

I looked at your code and it is quite elegant. Some questions:

• Why use object.__setattr__() in FormatterFuncsCaller __init__ instead of

  self.formatter = formatter

• What is the point of the recursive get_attribute() in FormatterFuncsCaller (line 892)? As far as I can see an instance of FormatterFuncsCaller doesn't have any attributes other than .formatter.
  EDIT: Never mind. It must be there to return .formatter and .call, at least
• What about not requiring the trailing '_' if there is no collision with a python keyword? FormatterFuncsCaller.__get_attribute__() could check the name with and without the underscore.
• Do we want the 'hidden' attributes .formatter and .funcs in PythonTemplateContext.attrs_set? I think these aren't something the user should use or see. No need for them to be in the output of __str__().
• This error exception should be simpler:
  

  EXCEPTION: Error in function evaluate on line 4 : AttributeError - 'FormatterFuncsCaller' object has no attribute 'a_python_template'

  Perhaps something like this:
  

  EXCEPTION: Error in function evaluate on line 4 : AttributeError - no function 'a_python_template' exists

• I am a little concerned about recursion in processing templates, but that can happen today. Oh well.

There are a few typos in comments, and a few cases where line spacing doesn't follow Kovid's rules. I can clean those up once we are satisfied with the implementation.