python - 使用 numpy.load 从文件中加载压缩数据 (.npz)

Question

我有一个数组：

>>> data = np.ones((1,3,128))

我使用以下方法将其保存到文件中savez_compressed：

>>> with open('afile','w') as f:
        np.savez_compressed(f,data=data)

当我尝试加载它时，我似乎无法访问数据：

>>> with open('afile','r') as f:
        b=np.load(f)
>>> b.files
['data']
>>> b['data']

Traceback (most recent call last):
  File "<pyshell#196>", line 1, in <module>
    b['data']
  File "C:\Python27\lib\site-packages\numpy\lib\npyio.py", line 238, in __getitem__
    bytes = self.zip.read(key)
  File "C:\Python27\lib\zipfile.py", line 828, in read
    return self.open(name, "r", pwd).read()
  File "C:\Python27\lib\zipfile.py", line 853, in open
    zef_file.seek(zinfo.header_offset, 0)
ValueError: I/O operation on closed file

我在做一些明显错误的事情吗？

编辑

在@Saullo Castro 的回答之后，我尝试了这个：

>>> np.savez_compressed('afile.npz',data=data)
>>> b=np.load('afile.npz')
>>> b.files
['data']
>>> b['data']

并得到以下错误：

Traceback (most recent call last):
  File "<pyshell#253>", line 1, in <module>
    b['data']
  File "C:\Python27\lib\site-packages\numpy\lib\npyio.py", line 241, in __getitem__
    return format.read_array(value)
  File "C:\Python27\lib\site-packages\numpy\lib\format.py", line 440, in read_array
    shape, fortran_order, dtype = read_array_header_1_0(fp)
  File "C:\Python27\lib\site-packages\numpy\lib\format.py", line 336, in read_array_header_1_0
    d = safe_eval(header)
  File "C:\Python27\lib\site-packages\numpy\lib\utils.py", line 1156, in safe_eval
    ast = compiler.parse(source, mode="eval")
  File "C:\Python27\lib\compiler\transformer.py", line 53, in parse
    return Transformer().parseexpr(buf)
  File "C:\Python27\lib\compiler\transformer.py", line 132, in parseexpr
    return self.transform(parser.expr(text))
  File "C:\Python27\lib\compiler\transformer.py", line 124, in transform
    return self.compile_node(tree)
  File "C:\Python27\lib\compiler\transformer.py", line 159, in compile_node
    return self.eval_input(node[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 194, in eval_input
    return Expression(self.com_node(nodelist[0]))
  File "C:\Python27\lib\compiler\transformer.py", line 805, in com_node
    return self._dispatch[node[0]](node[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 578, in testlist
    return self.com_binary(Tuple, nodelist)
  File "C:\Python27\lib\compiler\transformer.py", line 1082, in com_binary
    return self.lookup_node(n)(n[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 596, in test
    then = self.com_node(nodelist[0])
  File "C:\Python27\lib\compiler\transformer.py", line 805, in com_node
    return self._dispatch[node[0]](node[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 610, in or_test
    return self.com_binary(Or, nodelist)
  File "C:\Python27\lib\compiler\transformer.py", line 1082, in com_binary
    return self.lookup_node(n)(n[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 615, in and_test
    return self.com_binary(And, nodelist)
  File "C:\Python27\lib\compiler\transformer.py", line 1082, in com_binary
    return self.lookup_node(n)(n[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 619, in not_test
    result = self.com_node(nodelist[-1])
  File "C:\Python27\lib\compiler\transformer.py", line 805, in com_node
    return self._dispatch[node[0]](node[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 626, in comparison
    node = self.com_node(nodelist[0])
  File "C:\Python27\lib\compiler\transformer.py", line 805, in com_node
    return self._dispatch[node[0]](node[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 659, in expr
    return self.com_binary(Bitor, nodelist)
  File "C:\Python27\lib\compiler\transformer.py", line 1082, in com_binary
    return self.lookup_node(n)(n[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 663, in xor_expr
    return self.com_binary(Bitxor, nodelist)
  File "C:\Python27\lib\compiler\transformer.py", line 1082, in com_binary
    return self.lookup_node(n)(n[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 667, in and_expr
    return self.com_binary(Bitand, nodelist)
  File "C:\Python27\lib\compiler\transformer.py", line 1082, in com_binary
    return self.lookup_node(n)(n[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 671, in shift_expr
    node = self.com_node(nodelist[0])
  File "C:\Python27\lib\compiler\transformer.py", line 805, in com_node
    return self._dispatch[node[0]](node[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 683, in arith_expr
    node = self.com_node(nodelist[0])
  File "C:\Python27\lib\compiler\transformer.py", line 805, in com_node
    return self._dispatch[node[0]](node[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 695, in term
    node = self.com_node(nodelist[0])
  File "C:\Python27\lib\compiler\transformer.py", line 805, in com_node
    return self._dispatch[node[0]](node[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 715, in factor
    node = self.lookup_node(nodelist[-1])(nodelist[-1][1:])
  File "C:\Python27\lib\compiler\transformer.py", line 727, in power
    node = self.com_node(nodelist[0])
  File "C:\Python27\lib\compiler\transformer.py", line 805, in com_node
    return self._dispatch[node[0]](node[1:])
  File "C:\Python27\lib\compiler\transformer.py", line 739, in atom
    return self._atom_dispatch[nodelist[0][0]](nodelist)
  File "C:\Python27\lib\compiler\transformer.py", line 754, in atom_lbrace
    return self.com_dictorsetmaker(nodelist[1])
  File "C:\Python27\lib\compiler\transformer.py", line 1214, in com_dictorsetmaker
    assert nodelist[0] == symbol.dictorsetmaker
AssertionError

编辑 2

上述错误在 IDLE 中。它使用 Ipython 工作。

Answer 1

使用numpy.load时可以传文件名，如果扩展名是.npz，会先解压文件：

np.savez_compressed('filename.npz', array1=array1, array2=array2)
b = np.load('filename.npz')

等等b['array1']以从每个数组中检索数据...

Answer 2

您还可以使用该f属性，它会为您留下 np.ndarray：

images = np.load('images.npz')
images = images.f.arr_0

arr_0可以通过.npz 文件（例如 ）找到数组的名称/键

images.keys()

注意：该f属性未记录在 load 的文档字符串中。当 load 读取一个npz文件时，它会返回一个class NpzFile. 此类可作为numpy.lib.npyio.NpzFile. 类的文档字符串NpzFile描述了f属性。（在撰写本文时，可以在此处找到该类的源代码。

Answer 3

在 MAC OS 和 Windows 上使用 numpy 1.7.1/1.8.0 和 python 2.7.6 时，我确实遇到了同样的问题（AssertionError）。但是在我使用 python 2.7.5 切换到 linux 后，问题就自动修复了。然后我在 MACOS 和 Windows 上重新安装 python 2.7.5，所有问题都消失了。基本上问题在于python而不是numpy，因为编译器正在发送警报。所以版本可能很重要。

但是尽管 npy 是 numpy 的可序列化类型，但我认为即使 savez_compressed 用于大型矩阵，文件也不够小。

希望你的问题和我的一样

Answer 4

Try opening the file as binary:

with open('afile','rb') as f: