[Python-Dev] Inconsistent Use of Buffer Interface in stringobject.c

[Phil Thompson]

I'm implementing a string-like object in an extension module and trying to 
make it as interoperable with the standard string object as possible. To do 
this I'm implementing the relevant slots and the buffer interface. For most 
things this is fine, but there are a small number of methods in 
stringobject.c that don't use the buffer interface - and I don't understand 
why.

Specifically...

string_contains() doesn't which means that...

    MyString("foo") in "foobar"

...doesn't work.

s.join(sequence) only allows sequence to contain string or unicode objects.

s.strip([chars]) only allows chars to be a string or unicode object. Same for 
lstrip() and rstrip().

s.ljust(width[, fillchar]) only allows fillchar to be a string object (not 
even a unicode object). Same for rjust() and center().

Other methods happily allow types that support the buffer interface as well as 
string and unicode objects.

I'm happy to submit a patch - I just wanted to make sure that this behaviour 
wasn't intentional for some reason.

Thanks,
Phil