Not exactly sure what you mean by “auto fills the part”. But I can offer a few comments.
eeschema (the schematic editor) isn’t as accessible from python, but may not be necessary in this case.
You can add a part to eeschema and associate a footprint and it can automatically populate the PCB.
With the keyword substitution above, you might get the functionality you want. I have some ideas about making the substitution repeatable/updatable.
I don’t think bar codes are supported. I would expect “external fonts”, but those aren’t supported yet either (or at least as of 2015).
I’m sure a bar code python script could be developed.