See this issue:

https://github.com/numpy/numpy/issues/5543

There was also a very thorough discussion of this recently on this mailing list:

http://numpy-discussion.10968.n7.nabble.com/Proposal-to-support-format-td43931.html

On Tue, Feb 28, 2017 at 11:32 AM Ryan May <rmay31@gmail.com> wrote:
Hi,

Can someone take a look at: https://github.com/numpy/numpy/issues/7978

The crux of the issue is that this:

# This works
a = "%0.3g" % np.array(2)
a
'2'

# This does not
a = "{0:0.3g}".format(np.array(2))
TypeError: non-empty format string passed to object.__format__

I've now hit this in my code. If someone can even point me in the general direction of the code to dig into for this (please let it be python, please let it be python...), I'll dig in more.

Ryan

--
Ryan May

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