Another issue to consider here is that parsing and printing should be symmetrical. The %f format gobbles up exactly 6 digits.

Finally, strptime and strftime are not invented by Python, the same functions with (mostly) the same format characters are defined by other languages. Is there not a single other language that has added support for nanoseconds to its strftime/strptime? (I wouldn't be surprised if there wasn't -- while computer clocks have a precision in nanoseconds, that doesn't mean they are that *accurate* at all (even with ntpd running).