[Python-Dev] User conversions in custom string.Formatter

[Eric Smith]

On 03/15/2011 08:07 PM, Andrew Svetlov wrote:
> As PEP 3101 http://www.python.org/dev/peps/pep-3101/ says (and current
> Python does) user can specify conversions like "{0!s}".
> In custom formatters (derived from string.Formatter) he can override
> convert_field method to add custom conversions.
>
> I experimented with that last month and found it very convenient.
>> From my perspective custom conversions are very close to 'filters'
> from html template engines (jinja2, mako, django etc).
> While I like to see custom conversions simple and easy I don't wan't
> to bring 'cascading' and 'parametrization' to standard formatting.
>
> But why don't relax spec a bit and allow to use any word (with
> 'identifier' semantix, I mean str.isidentifier()) as conversion name?
> Proposed update doesn't make any backward incompatibility (both python
> and public C API are not changed), it's clean and obvious.
> And it's very funny to use words instead single characters for custom
> user-specific conversions.
>
> What do you think?

This should be in python-ideas, but I don't know if Andrew is 
subscribed, so I'll reply here until it gets out of control.

Andrew: Could you give a code sample of what you'd like to see?

Eric.