[Python-Dev] transitioning from % to {} formatting

Martin Geisler mg at lazybytes.net
Fri Oct 2 21:43:48 CEST 2009

"Raymond Hettinger" <python at rcn.com> writes:

> [Steven Bethard]
>>. Just saying "ok, switch your format strings
>> from % to {}" didn't work in Python 3.0 for various good reasons, and
>> I can't imagine it will work in Python 4.0 unless we have a transition
>> plan.
> Do the users get any say in this?

I'm a user! :-)

I hate calling methods on string literals, I think it looks very odd to
have code like this:

  "Displaying {0} of {1} revisions".format(x, y)

Will we be able to write this as

  "Displaying {0} of {1} revisions" % (x, y)


> I imagine that some people are heavily invested in %-formatting.
> Because there has been limited uptake on {}-formatting (afaict), we
> still have limited experience with knowing that it is actually better,
> less error-prone, easier to learn/rember, etc. Outside a handful of
> people on this list, I have yet to see anyone adopt it as the
> preferred syntax.

I've skimmed over the PEP, and the new {}-syntax seems to have some nice
features. But I've not seen it used anywhere yet.

Martin Geisler

VIFF (Virtual Ideal Functionality Framework) brings easy and efficient
SMPC (Secure Multiparty Computation) to Python. See: http://viff.dk/.
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