* .npy中数据的存储方式是什么? [英] What is the way data is stored in *.npy?

问题描述

我正在使用numpy.save函数保存NumPy数组. 我希望其他开发人员能够使用C语言从这些文件中读取数据. 所以我需要知道numpy如何在file中组织二进制数据.好吧，当我保存'i4'数组时很明显，但是包含某些结构的数组又如何呢?在文档中找不到任何信息

I'm saving NumPy arrays using numpy.save function. I want other developers to have capability to read data from those file using C language. So I need to know,how numpy organizes binary data in file.OK, it's obvious when I'm saving array of 'i4' but what about array of arrays that contains some structures?Can't find any info in documentation

UPD: 可以说tha数据类似于:

UPD : lets say tha data is something like :

dt = np.dtype([('outer','(3,)<i4'),('outer2',[('inner','(10,)<i4'),('inner2','f8')])])

UPD2:如何保存动态"数据(dtype-对象)

UPD2 : What about saving "dynamic" data (dtype - object)

import numpy as np
a = [0,0,0]
b = [0,0]
c = [a,b]
dtype = np.dtype([('Name', '|S2'), ('objValue', object)])
data = np.zeros(3, dtype)
data[0]['objValue'] = a
data[1]['objValue'] = b
data[2]['objValue'] = c
data[0]['Name'] = 'a'
data[1]['Name'] = 'b'
data[2]['Name'] = 'c'

np.save(r'D:\in.npy', data)

从C那里读那个东西真的吗?

Is it real to read that thing from C?

推荐答案

npy文件格式记录在numpy的

The npy file format is documented in numpy's NEP 1 — A Simple File Format for NumPy Arrays.

例如，代码

>>> dt=numpy.dtype([('outer','(3,)<i4'),
...                 ('outer2',[('inner','(10,)<i4'),('inner2','f8')])])
>>> a=numpy.array([((1,2,3),((10,11,12,13,14,15,16,17,18,19),3.14)),
...                ((4,5,6),((-1,-2,-3,-4,-5,-6,-7,-8,-9,-20),6.28))],dt)
>>> numpy.save('1.npy', a)

产生文件:

93 4E 55 4D 50 59                      magic ("\x93NUMPY")
01                                     major version (1)
00                                     minor version (0)

96 00                                  HEADER_LEN (0x0096 = 150)
7B 27 64 65 73 63 72 27 
3A 20 5B 28 27 6F 75 74 
65 72 27 2C 20 27 3C 69 
34 27 2C 20 28 33 2C 29 
29 2C 20 28 27 6F 75 74 
65 72 32 27 2C 20 5B 28 
27 69 6E 6E 65 72 27 2C 
20 27 3C 69 34 27 2C 20 
28 31 30 2C 29 29 2C 20 
28 27 69 6E 6E 65 72 32                Header, describing the data structure
27 2C 20 27 3C 66 38 27                "{'descr': [('outer', '<i4', (3,)),
29 5D 29 5D 2C 20 27 66                            ('outer2', [
6F 72 74 72 61 6E 5F 6F                               ('inner', '<i4', (10,)), 
72 64 65 72 27 3A 20 46                               ('inner2', '<f8')]
61 6C 73 65 2C 20 27 73                            )],
68 61 70 65 27 3A 20 28                  'fortran_order': False,
32 2C 29 2C 20 7D 20 20                  'shape': (2,), }"
20 20 20 20 20 20 20 20 
20 20 20 20 20 0A 

01 00 00 00 02 00 00 00 03 00 00 00    (1,2,3)
0A 00 00 00 0B 00 00 00 0C 00 00 00
0D 00 00 00 0E 00 00 00 0F 00 00 00
10 00 00 00 11 00 00 00 12 00 00 00
13 00 00 00                            (10,11,12,13,14,15,16,17,18,19)
1F 85 EB 51 B8 1E 09 40                3.14

04 00 00 00 05 00 00 00 06 00 00 00    (4,5,6)
FF FF FF FF FE FF FF FF FD FF FF FF
FC FF FF FF FB FF FF FF FA FF FF FF
F9 FF FF FF F8 FF FF FF F7 FF FF FF 
EC FF FF FF                            (-1,-2,-3,-4,-5,-6,-7,-8,-9,-20)
1F 85 EB 51 B8 1E 19 40                6.28

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