Re: [Numpy-discussion] numpy datetime64 NaT string conversion bug patch

[Julian Taylor]

On 27.11.2013 21:51, Charles G. Waldman wrote:
 If you convert an array of strings to datetime64s and 'NaT' (or one of
 its variants) appears in the string, all subsequent values are
 rendered as NaT:

thanks, a little embarrassing I didn't spot that when I fixed a
different bug in the function recently :/

do you want to create a pull request with the fix?
see http://docs.scipy.org/doc/numpy/dev/gitwash/development_workflow.html
add a testcase too, numpy/core/tests/test_datetime.py is probably the
right place.
Feel free to answer you don't have time for doing a PR.
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[Numpy-discussion] numpy datetime64 NaT string conversion bug patch

[Charles G. Waldman]

If you convert an array of strings to datetime64s and 'NaT' (or one of
its variants) appears in the string, all subsequent values are
rendered as NaT:

(this is in 1.7.1 but the problem is present in current dev version as well)

 import numpy as np
 a = np.array(['2010', 'nat', '2030'])
 a.astype(np.datetime64)
array(['2010', 'NaT', 'NaT'], dtype='datetime64[Y]')

The fix is to re-initalize 'dt' inside the loop in
_strided_to_strided_string_to_datetime
(patch attached)



Correct behavior (with patch):
 import numpy as np
 a=np.array(['2010', 'nat', '2020'])
 a.astype(np.datetime64)
array(['2010', 'NaT', '2020'], dtype='datetime64[Y]')

diff --git a/numpy/core/src/multiarray/dtype_transfer.c b/numpy/core/src/multiarray/dtype_transfer.c
index f758139..3bd362c 100644
--- a/numpy/core/src/multiarray/dtype_transfer.c
+++ b/numpy/core/src/multiarray/dtype_transfer.c
@@ -884,12 +884,13 @@ _strided_to_strided_string_to_datetime(char *dst, npy_intp dst_stride,
 NpyAuxData *data)
 {
 _strided_datetime_cast_data *d = (_strided_datetime_cast_data *)data;
-npy_int64 dt = ~NPY_DATETIME_NAT;
 npy_datetimestruct dts;
 char *tmp_buffer = d-tmp_buffer;
 char *tmp;
 
 while (N  0) {
+npy_int64 dt = ~NPY_DATETIME_NAT;
+
 /* Replicating strnlen with memchr, because Mac OS X lacks it */
 tmp = memchr(src, '\0', src_itemsize);
 
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