蟒蛇：如何添加列记录numpy的阵列 [英] python: how to add column to record array in numpy

问题描述

我想一列添加到numpy的记录。

I am trying to add a column to a numpy record.

这是我的code：

import numpy
import numpy.lib.recfunctions
data=[[20140101,'a'],[20140102,'b'],[20140103,'c']]
data_array=numpy.array(data)
data_dtype=[('date',int),('type','|S1')]
data_rec=numpy.core.records.array(list(tuple(data_array.transpose())), dtype=data_dtype)
data_rec.date
data_rec.type

#Here, i will just try to make another field called copy_date that is a copy of the date    , just as an example

y=numpy.lib.recfunctions.append_fields(data_rec,'copy_date',data_rec.date,dtypes=data_rec.date.dtype,usemask=False)

现在看一下输出

>>> type(y)
<type 'numpy.ndarray'>
>>> y.date
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'numpy.ndarray' object has no attribute 'date'
>>> y.copy_date
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'numpy.ndarray' object has no attribute 'copy_date'

y是不再像

>>> type(data_rec)
<class 'numpy.core.records.recarray'>

我似乎失去记录的能力，这是调用由属性的字段。
我该如何正确列添加到一个记录，并能够调用的领域？

I seem to have lost the record abilities, which is to call the fields by the attribute. How can I correctly add a column to a record and be able to call the fields?

另外，我会很高兴，如果有人能告诉我usemask选项确实在上述code的内容。

Also, I'd be happy if someone can tell me what the usemask option does in the above code.

感谢

推荐答案

您可以通过 asrecarray = TRUE 来得到一个recarray背出 numpy的的.lib.recfunctions.append_fields 。

You can pass asrecarray=True to get a recarray back out of numpy.lib.recfunctions.append_fields.

例如：

>>> y = numpy.lib.recfunctions.append_fields(data_rec, 'copy_date', data_rec.date, dtypes=data_rec.date.dtype, usemask=False, asrecarray=True)
>>> y.date
array([2, 2, 2])
>>> y
rec.array([(2, 'a', 2), (2, 'b', 2), (2, 'c', 2)], 
      dtype=[('date', '<i8'), ('type', '|S1'), ('copy_date', '<i8')])
>>> y.copy_date
array([2, 2, 2])

的测试在numpy的1.6.1 的

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