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我正在尝试使用 python 切片对象使用h5py模块访问 HDF5 文件中的数据。我把这个例子放在一起来说明它适用于numpy数组，但不适用于h5py.

import h5py
import numpy as np

slice_obj = [slice(None,3,None), slice(2,5,None)]

test_array = np.ones((3,5))
print test_array[0:3,2:5]
print test_array[slice_obj]

f = h5py.File("testing.hdf5","w")
f['data'] = test_array
f.close()

f = h5py.File("testing.hdf5","r")
test2 = f['data'][0:3,2:5]
print test2
test2 = f['data'][slice_obj]
print test2
f.close()

这给出了以下输出：

[[ 1.  1.  1.]
 [ 1.  1.  1.]
 [ 1.  1.  1.]]
[[ 1.  1.  1.]
 [ 1.  1.  1.]
 [ 1.  1.  1.]]
[[ 1.  1.  1.]
 [ 1.  1.  1.]
 [ 1.  1.  1.]]
Traceback (most recent call last):
  File "slice.py", line 17, in <module>
    test2 = f['data'][slice_obj]
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/h5py/_hl/dataset.py", line 439, in __getitem__
    self.id.read(mspace, fspace, arr, mtype)
  File "h5d.pyx", line 179, in h5py.h5d.DatasetID.read (h5py/h5d.c:2479)
  File "_proxy.pyx", line 118, in h5py._proxy.dset_rw (h5py/_proxy.c:1300)
  File "_proxy.pyx", line 84, in h5py._proxy.H5PY_H5Dread (h5py/_proxy.c:1051)
IOError: can't read data (Dataset: Read failed)

有谁知道这是否不可能h5py？如果不是，是否有另一种方法来切片h5py，使用对象或变量，而不是像f['data'][0:3,2:5]我的示例中那样显式键入切片？

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1 回答 1

5

玩弄你的例子：

test2 = f['data']
print test2
print test2.shape
print test2[0:3,2:5]
print test2[slice(None,3,None),slice(2,5,None)]  # ok
print test2[slice_obj[0],slice_obj[1]]  # ok
print test2[tuple(slice_obj)]  # ok
print test2[[slice(None,3,None),slice(2,5,None)]]  # fail
print f['data'][tuple(slice_obj)] 3 ok

所以看起来h5py数组可以使用切片，但不能将列表拆分为其元素。但它确实需要一个元组。我的猜测是实现方式存在细微差别getitem。

您正在执行高级索引。 numpy医生说：

Advanced indexing is triggered when the selection object, obj,... a tuple with at least one sequence object.... when the selection object is not a tuple, it will be referred to as if it had been promoted to a 1-元组，这将被称为选择元组。

h5py可能不会这样做促进元组。否则，它似乎可以很好地进行高级索引。

于 2013-12-11T18:21:21.623 回答