8000 ENH: Add support for float hex format to loadtxt. by charris · Pull Request #5504 · numpy/numpy · GitHub
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ENH: Add support for float hex format to loadtxt. #5504

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Merged
merged 3 commits into from
Feb 13, 2015
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ENH: Add support for float hex format to loadtxt. #5504

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4aef6a8
ENH: Add support for float hex format to loadtxt.
claumann Aug 4, 2011
31f5d40
TST: Make loadtxt able to load floats as hex strings.
charris Feb 12, 2015
0516465
DOC: Document loadtxt support for float.hex float representation.
charris Feb 12, 2015
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5 changes: 5 additions & 0 deletions doc/release/1.10.0-notes.rst
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Expand Up @@ -139,6 +139,11 @@ fallback implementations of the following functions.
As a result of these improvements, there will be some small changes in
returned values, especially for corner cases.

*np.loadtxt* support for the strings produced by the ``float.hex`` method
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The strings produced by ``float.hex`` look like ``0x1.921fb54442d18p+1``,
so this is not the hex used to represent unsigned integer types.


Changes
=======
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13 changes: 12 additions & 1 deletion numpy/lib/npyio.py
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Expand Up @@ -621,6 +621,13 @@ def _savez(file, args, kwds, compress):

def _getconv(dtype):
""" Find the correct dtype converter. Adapted from matplotlib """

def floatconv(x):
x.lower()
if b'0x' in x:
return float.fromhex(asstr(x))
return float(x)

typ = dtype.type
if issubclass(typ, np.bool_):
return lambda x: bool(int(x))
Expand All @@ -631,7 +638,7 @@ def _getconv(dtype):
if issubclass(typ, np.integer):
return lambda x: int(float(x))
elif issubclass(typ, np.floating):
return float
return floatconv
elif issubclass(typ, np.complex):
return complex
elif issubclass(typ, np.bytes_):
Expand Down Expand Up @@ -706,6 +713,10 @@ def loadtxt(fname, dtype=float, comments='#', delimiter=None,
`genfromtxt` function provides more sophisticated handling of, e.g.,
lines with missing values.

.. versionadded:: 1.10.0
The strings produced by the Python float.hex method can be used as
input for floats.

Examples
--------
>>> from StringIO import StringIO # StringIO behaves like a file object
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13 changes: 13 additions & 0 deletions numpy/lib/tests/test_io.py
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Expand Up @@ -694,6 +694,19 @@ def test_int64_type(self):
res = np.loadtxt(c, dtype=np.int64)
assert_equal(res, tgt)

def test_from_float_hex(self):
# IEEE doubles and floats only, otherwise the float32
# conversion may fail.
tgt = np.logspace(-10, 10, 5).astype(np.float32)
tgt = np.hstack((tgt, -tgt)).astype(np.float)
inp = '\n'.join(map(float.hex, tgt))
c = TextIO()
c.write(inp)
for dt in [np.float, np.float32]:
c.seek(0)
res = np.loadtxt(c, dtype=dt)
assert_equal(res, tgt, err_msg="%s" % dt)

def test_universal_newline(self):
f, name = mkstemp()
os.write(f, b'1 21\r3 42\r')
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