如何将numpy.savetxt与包含数组的结构化数组一起使用 [英] How to use numpy.savetxt with a structured array that contains an array
问题描述
说我有一个结构化数组,如下所示:
Say I have a structured array as follows:
a = np.zeros(10,dtype=[('label1',np.int32, 4), ('label2', np.float_)])
然后我尝试将其另存为csv文件:
And I try to save this as a csv file:
np.savetxt('output.csv', a, fmt='%d,%d,%d,%d,%f')
Python会产生此错误:
Python will generate this error:
ValueError: fmt has wrong number of % formats: %d,%d,%d,%d,%f
我无法创建适合我的输出的fmt字符串.%s在这里对我不起作用,因为我需要能够指定浮点数的格式.
I haven't been able to create a fmt string that would suit my output. %s won't work for me here as I need the ability specify the format of the float.
是否可以通过这种类型的结构化数组创建csv文件?
Is it possible to create a csv file from this type of structured array?
推荐答案
本质上, savetxt
的作用是:
for row in arr:
print(fmt % tuple(row))
因此, fmt
必须与 row
,或者在这种情况下,是数组的元素一起使用.
So the fmt
has to work with a row
, or in this case, an element of your array.
In [330]: a = np.zeros(10,dtype=[('label1',np.int32, 4), ('label2', np.float_)])
...:
In [331]: a
Out[331]:
array([([0, 0, 0, 0], 0.), ([0, 0, 0, 0], 0.), ([0, 0, 0, 0], 0.),
([0, 0, 0, 0], 0.), ([0, 0, 0, 0], 0.), ([0, 0, 0, 0], 0.),
([0, 0, 0, 0], 0.), ([0, 0, 0, 0], 0.), ([0, 0, 0, 0], 0.),
([0, 0, 0, 0], 0.)],
dtype=[('label1', '<i4', (4,)), ('label2', '<f8')])
In [332]: a[0]
Out[332]: ([0, 0, 0, 0], 0.)
In [333]: tuple(a[0])
Out[333]: (array([0, 0, 0, 0]), 0.0)
在 label1
中嵌套4个int使得很难提出一种有效的格式.这与如何使用Python'%'格式有关.
Nesting the 4 ints in label1
makes it difficult to come up with a format that works. It's a matter of how to Python '%' formatting.
In [334]: '%s, %f'%_
Out[334]: '[0 0 0 0], 0.000000'
如果 a
是5个字段,则会更容易
If a
was 5 fields it would be easier
In [335]: a = np.zeros(10,dtype='i,i,i,i,f')
In [336]: a
Out[336]:
array([(0, 0, 0, 0, 0.),....
(0, 0, 0, 0, 0.)],
dtype=[('f0', '<i4'), ('f1', '<i4'), ('f2', '<i4'), ('f3', '<i4'), ('f4', '<f4')])
In [337]: tuple(a[0])
Out[337]: (0, 0, 0, 0, 0.0)
In [338]: '%d, %d, %d, %d, %f'%tuple(a[0])
Out[338]: '0, 0, 0, 0, 0.000000'
我认为您需要展平"阵列的结构,或编写自定义的 savetxt
.正如我指出的那样, savetxt
并不理想.如果您可以按所需格式逐元素 print
数组元素,则可以将该格式写入文件.
I think you need to either 'flatten' the structure of your array, or write a custom savetxt
. As I indicated savetxt
is not fancy. If you can print
the array element by element in the format you want, you can write that format to a file.
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