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NumPy genfromtxt列定义

pythonnumpygenfromtxt
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我在使用numpy genfromtxt时遇到了一个看似非常简单的问题。以下是我的代码（非常简化版）：

import numpy as np

in_file_1 = raw_input ('enter name of template file to be scaled:\n')
spec_1 = np.genfromtxt(in_file_1, delimiter = [8,24], dtype =float)
print spec_1

我正在读取的文件非常简单，只有两列，没有标题等内容：
6392.01   0.90286163
6392.05   0.88731778
6392.09   0.87789831
6392.13   0.87716535
6392.16   0.88523003
6392.20   0.90948176
6392.24   0.93056874
6392.28   0.95782283
6392.32   0.98056805
6392.36   0.99623797
6392.39   0.99458828
6392.43   0.9848269
6392.47   0.96011146
6392.51   0.92864767

当我在Python命令行中使用genfromtxt读取以上内容时，它会按照我的期望给出一个两列的数组：

>>> import numpy as np
>>> in_file_1 = raw_input ('enter name of template file to be scaled:\n')
enter name of template file to be scaledl_1714650_052_no_head.txt
>>> spec_1 = np.genfromtxt(in_file_1, delimiter = [8,24], dtype =float)
>>> spec_1
array([[  6.39201000e+03,   9.02861630e-01],
       [  6.39205000e+03,   8.87317780e-01],
       [  6.39209000e+03,   8.77898310e-01],
       [  6.39213000e+03,   8.77165350e-01],
       [  6.39216000e+03,   8.85230030e-01],
       [  6.39220000e+03,   9.09481760e-01],
       [  6.39224000e+03,   9.30568740e-01],
       [  6.39228000e+03,   9.57822830e-01],
       [  6.39232000e+03,   9.80568050e-01],
       [  6.39236000e+03,   9.96237970e-01],
       [  6.39239000e+03,   9.94588280e-01],
       [  6.39243000e+03,   9.84826900e-01],
       [  6.39247000e+03,   9.60111460e-01],
       [  6.39251000e+03,   9.28647670e-01]])
>>>

但是当我将这个脚本（read_test.py）作为本文顶部的脚本运行时，它返回一个字符串的单列：
[scrooge:Acc_cont_removal/All_stars/Test] darryl% python read_test.py 
enter name of template file to be scaled:
l_1714650_052_no_head.txt
[[  6.39201000e+03   9.02861630e-01]
 [  6.39205000e+03   8.87317780e-01]
 [  6.39209000e+03   8.77898310e-01]
 [  6.39213000e+03   8.77165350e-01]
 [  6.39216000e+03   8.85230030e-01]
 [  6.39220000e+03   9.09481760e-01]
 [  6.39224000e+03   9.30568740e-01]
 [  6.39228000e+03   9.57822830e-01]
 [  6.39232000e+03   9.80568050e-01]
 [  6.39236000e+03   9.96237970e-01]
 [  6.39239000e+03   9.94588280e-01]
 [  6.39243000e+03   9.84826900e-01]
 [  6.39247000e+03   9.60111460e-01]
 [  6.39251000e+03   9.28647670e-01]]
[scrooge:Acc_cont_removal/All_stars/Test] darryl%

我已经尝试了各种分隔符等配置，但我无法弄清楚发生了什么问题，而这段代码在几天前还可以正常运行。在OSX（Lion）上运行，使用的是Python v2.7。

非常感谢您的任何想法。 达里尔

那看起来不像是一个字符串列。实际上，它几乎与正确的输出完全相同。 - huon
但是，当我尝试引用它时，比如：a = spec_1[0:1]，它没有返回任何值。我可以引用行（比如 a = spec[1]），这将返回整行，但不能返回单个元素。 - Darryl Sergison
spec_1[1] 应该返回整行，如果你想要单独的元素，可以使用 spec_1[1,0]，spec_1[2,1] 等。另外，如果你在 test_read.py 的结尾添加 print spec_1.dtype, spec_1.shape，你会得到什么输出？我得到的是 float64 (14, 2)。 - huon
1个回答
4
你得到的正是你应该得到的答案！
>>> numpy.genfromtxt('testfile', delimiter=[8,24], dtype = float)
array([[  6.39201000e+03,   9.02861630e-01],
       [  6.39205000e+03,   8.87317780e-01],
       [  6.39209000e+03,   8.77898310e-01],
       [  6.39213000e+03,   8.77165350e-01],
       [  6.39216000e+03,   8.85230030e-01],
       [  6.39220000e+03,   9.09481760e-01],
       [  6.39224000e+03,   9.30568740e-01],
       [  6.39228000e+03,   9.57822830e-01],
       [  6.39232000e+03,   9.80568050e-01],
       [  6.39236000e+03,   9.96237970e-01],
       [  6.39239000e+03,   9.94588280e-01],
       [  6.39243000e+03,   9.84826900e-01],
       [  6.39247000e+03,   9.60111460e-01],
       [  6.39251000e+03,   9.28647670e-01]])
>>> print _
[[  6.39201000e+03   9.02861630e-01]
 [  6.39205000e+03   8.87317780e-01]
 [  6.39209000e+03   8.77898310e-01]
 [  6.39213000e+03   8.77165350e-01]
 [  6.39216000e+03   8.85230030e-01]
 [  6.39220000e+03   9.09481760e-01]
 [  6.39224000e+03   9.30568740e-01]
 [  6.39228000e+03   9.57822830e-01]
 [  6.39232000e+03   9.80568050e-01]
 [  6.39236000e+03   9.96237970e-01]
 [  6.39239000e+03   9.94588280e-01]
 [  6.39243000e+03   9.84826900e-01]
 [  6.39247000e+03   9.60111460e-01]
 [  6.39251000e+03   9.28647670e-01]]

这只是打印和获取结果表示之间的区别。

>>> result = numpy.genfromtxt('testfile', delimiter=[8,24], dtype = float)
>>> repr(result)
'array([[  6.39201000e+03,   9.02861630e-01],\n       [  6.39205000e+03,   8.87317780e-01],\n       [  6.39209000e+03,   8.77898310e-01],\n       [  6.39213000e+03,   8.77165350e-01],\n       [  6.39216000e+03,
  8.85230030e-01],\n       [  6.39220000e+03,   9.09481760e-01],\n       [  6.39224000e+03,   9.30568740e-01],\n       [  6.39228000e+03,   9.57822830e-01],\n       [  6.39232000e+03,   9.80568050e-01],\n
[  6.39236000e+03,   9.96237970e-01],\n       [  6.39239000e+03,   9.94588280e-01],\n       [  6.39243000e+03,   9.84826900e-01],\n       [  6.39247000e+03,   9.60111460e-01],\n       [  6.39251000e+03,   9.2864
7670e-01]])'

>>> str(result)
'[[  6.39201000e+03   9.02861630e-01]\n [  6.39205000e+03   8.87317780e-01]\n [  6.39209000e+03   8.77898310e-01]\n [  6.39213000e+03   8.77165350e-01]\n [  6.39216000e+03   8.85230030e-01]\n [  6.39220000e+03
 9.09481760e-01]\n [  6.39224000e+03   9.30568740e-01]\n [  6.39228000e+03   9.57822830e-01]\n [  6.39232000e+03   9.80568050e-01]\n [  6.39236000e+03   9.96237970e-01]\n [  6.39239000e+03   9.94588280e-01]\n [
 6.39243000e+03   9.84826900e-01]\n [  6.39247000e+03   9.60111460e-01]\n [  6.39251000e+03   9.28647670e-01]]'

注意，str版本没有逗号，而repr版本有逗号吗？
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