[Python-Dev] Can I modify string.Formatter._vformat?

[Eric Smith]

I'm implementing support for auto-numbering of str.format() fields (see 
http://bugs.python.org/issue5237). I'm reasonably sure that when I'm 
done modifying the C implementation I'll need to change the signatures 
of string.Formatter._vformat, str._formatter_parser, and/or 
str._formatter_field_name_split. (They need to support the state needed 
to track the auto-number field counter.)

I've always considered these internal implementation details of 
str.format and string.Formatter. They begin with underscores and are not 
documented.

Is there any problem with modifying these in 2.7 and 3.1? I assume not, 
but I want to make sure it doesn't give anyone heartburn.

Eric.