[Numpy-discussion] floats coerced to string with "{:f}".format() ?

Maccarthy, Jonathan K jkmacc at lanl.gov
Thu Jun 6 16:50:42 EDT 2013

I'm really showing my ignorance now, I think;  so, the old-style "fmt % (tuple)" must use a different mechanism, and perhaps that's why np.savetxt never choked on a float32 for me before (yes, I am on a 64-bit system).

In [8]: type(tmp.lat)
Out[8]: numpy.float32

In [9]: '%6s %8i %11.6f' % (tmp.sta, tmp.ondate, tmp.lat)
Out[9]: '  XYZZ  2001123  -23.820000'

Thanks again for your patience.

On Jun 6, 2013, at 2:26 PM, Robert Kern wrote:

> np.float64 works because it inherits from the Python float type
> (Python floats are 64-bit floats). np.float32 doesn't inherit from the
> Python float type because it can't; they don't represent the same kind
> of data, so their memory layouts at the C level cannot coincide. Since
> you are on a 64-bit platform, np.int64 represents the same kind of
> integer as the Python int type, so it can subclass, but an np.int32
> couldn't.
> It's not necessarily intuitive, but it's the best we can do under the
> constraints. The only thing more intuitive would be to disallow
> subclassing from the Python builtin types entirely, but that's
> *really* annoying.
> --
> Robert Kern
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