如何更改numpy recarray的某些列的dtype?

问题描述

假设我有一个如下的recarray:

Suppose I have a recarray such as the following:

import numpy as np

# example data from @unutbu's answer
recs = [('Bill', '31', 260.0), ('Fred', 15, '145.0')]
r = np.rec.fromrecords(recs, formats = 'S30,i2,f4', names = 'name, age, weight')

print(r)
# [('Bill', 31, 260.0) ('Fred', 15, 145.0)]

说我想将某些列转换为浮点数.我该怎么做呢?我应该更改为ndarray并将其重新返回为recarray吗?

Say I want to convert certain columns to floats. How do I do this? Should I change to an ndarray and them back to a recarray?

推荐答案

以下是使用astype进行转换的示例:

Here is an example using astype to perform the conversion:

import numpy as np
recs = [('Bill', '31', 260.0), ('Fred', 15, '145.0')]
r = np.rec.fromrecords(recs, formats = 'S30,i2,f4', names = 'name, age, weight')
print(r)
# [('Bill', 31, 260.0) ('Fred', 15, 145.0)]

age具有dtype <i2:

print(r.dtype)
# [('name', '|S30'), ('age', '<i2'), ('weight', '<f4')]

我们可以使用astype将其更改为<f4:

We can change that to <f4 using astype:

r = r.astype([('name', '|S30'), ('age', '<f4'), ('weight', '<f4')])
print(r)
# [('Bill', 31.0, 260.0) ('Fred', 15.0, 145.0)]

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