[Python-Dev] transitioning from % to {} formatting (original) (raw)

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)

too?

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

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