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Can anyone tell me why this NumPy record is having trouble with Python's new-style string formatting? All floats in the record choke on "{:f}".format(record).

Thanks for your help!

In [334]: type(tmp)
Out[334]: numpy.core.records.record

In [335]: tmp
Out[335]: ('XYZZ', 2001123, -23.823917388916016)

In [336]: tmp.dtype
Out[336]: dtype([('sta', '|S6'), ('ondate', '<i8'), ('lat', '<f4')])

# Some formatting works fine
In [337]: '{0.sta:6.6s} {0.ondate:8d}'.format(tmp)
Out[337]: 'XYZZ    2001123'

# Any float has trouble
In [338]: '{0.sta:6.6s} {0.ondate:8d} {0.lat:11.6f}'.format(tmp)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/Users/jkmacc/python/pisces/<ipython-input-338-e5f6bcc4f60f> in <module>()
----> 1 '{0.sta:6.6s} {0.ondate:8d} {0.lat:11.6f}'.format(tmp)

ValueError: Unknown format code 'f' for object of type 'str'
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1 Answer

up vote 0 down vote

Maybe I am missing some catch, but it seems that you can only use {something:s}. I tried some examples and even using only float records:

tmp = (1.1, 1111, 2001123, -23.823917388916016)

tmp = numpy.array(tmp, dtype=[('test',float), ('sta',float), ('ondate,float), ('lat',float)])

the following is all right:

'{0[test]:s} {0[sta]:10s} {0[ondate]} {0[lat]:10.7s}'.format(tmp)
#'1.1 1111.0     2001123.0 -23.823   '

but this does not work:

'{0[test]:s} {0[sta]:10s} {0[ondate]} {0[lat]:10.7f}'.format(tmp)
#ValueError: Unknown format code 'f' for object of type 'str'
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