Thanks for bringing this up. I asked about this on reddit yesterday[1] and was linked the thread where they originally discussed this[2]. Basically, the goal is to make porting from 2 to 3 easier, and there's also a notion that printf-style formatting may be more natural than format-style formatting for bytes.

I still wish they were consistent and provided a .format method for bytes, especially since, as you point out, .format was supposed to be the "new way" to do formatting and this feels like a step backwards. And what about backward compatibility for porting Python 2 code that used .format to do formatting on what are semantically byte strings?

[1] https://www.reddit.com/r/Python/comments/3c7lne/python_350b3...

[2] http://thread.gmane.org/gmane.comp.python.devel/144712/focus...

As long as % formatting still works, it is in many ways more convenient that format. '"Foo: %s" % bar' is a lot shorter to write than '"Foo: {}".format(bar)'. And % formatting is still built into logger, so if you use logger heavily you will probably be used to it.

While the format() mini-language is nicer in a lot of ways, the convenience of % and its ubiquity mean that I generally use it more often. The main time when I reach for format() is when I need more detailed control of column widths and the like, which you can do with things like "{var:{width}}".format(var=var, width=width)

If you read the PEP, it explains how they are adding it for easier python2 -> python3 migration