pandas 如何在 Python3 中解码编码文字/字符串的 numpy 数组？AttributeError: 'numpy.ndarray' 对象没有属性 'decode'
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How to decode a numpy array of encoded literals/strings in Python3? AttributeError: 'numpy.ndarray' object has no attribute 'decode'
提问by ShanZhengYang
In Python 3, I have the follow NumPyarray of strings.
在Python 3，我有如下NumPy的阵列strings。
Each stringin the NumPyarray is in the form b'MD18EEinstead of MD18EE.
每个string中NumPy阵列的形式b'MD18EE，而不是MD18EE。
For example:
例如：
import numpy as np
print(array1)
(b'first_element', b'element',...)
Normally, one would use .decode('UTF-8')to decode these elements.
通常，人们会使用.decode('UTF-8')解码这些元素。
However, if I try:
但是，如果我尝试：
array1 = array1.decode('UTF-8')
I get the following error:
我收到以下错误：
AttributeError: 'numpy.ndarray' object has no attribute 'decode'
How do I decode these elements from a NumPyarray? (That is, I don't want b'')
如何从NumPy数组中解码这些元素？（也就是说，我不想b''）
EDIT:
编辑：
Let's say I was dealing with a PandasDataFramewith only certain columns that were encoded in this manner. For example:
假设我只处理以PandasDataFrame这种方式编码的某些列。例如：
import pandas as pd
df = pd.DataFrame(...)
df
COL1 ....
0 b'entry1' ...
1 b'entry2'
2 b'entry3'
3 b'entry4'
4 b'entry5'
5 b'entry6'
回答by hpaulj
You have an array of bytestrings; dtype is S:
你有一个字节串数组；数据类型是S：
In [338]: arr=np.array((b'first_element', b'element'))
In [339]: arr
Out[339]:
array([b'first_element', b'element'],
dtype='|S13')
astypeeasily converts them to unicode, the default string type for Py3.
astype轻松将它们转换为 unicode，这是 Py3 的默认字符串类型。
In [340]: arr.astype('U13')
Out[340]:
array(['first_element', 'element'],
dtype='<U13')
There is also a library of string functions - applying the corresponding strmethod to the elements of a string array
还有一个字符串函数库——将相应的str方法应用于字符串数组的元素
In [341]: np.char.decode(arr)
Out[341]:
array(['first_element', 'element'],
dtype='<U13')
The astypeis faster, but the decodelets you specify an encoding.
的astype速度更快，但decode允许您指定的编码。
See also How to decode a numpy array of dtype=numpy.string_?
回答by Wander Nauta
If you want the result to be a (Python) list of strings, you can use a list comprehension:
如果您希望结果是一个 (Python) 字符串列表，您可以使用列表理解：
>>> l = [el.decode('UTF-8') for el in array1]
>>> print(l)
['element', 'element 2']
>>> print(type(l))
<class 'list'>
Alternatively, if you want to keep it as a Numpy array, you can use np.vectorizeto make a vectorized decoder function:
或者，如果您想将其保留为 Numpy 数组，则可以使用np.vectorize来制作矢量化解码器函数：
>>> decoder = np.vectorize(lambda x: x.decode('UTF-8'))
>>> array2 = decoder(array1)
>>> print(array2)
['element' 'element 2']
>>> print(type(array2))
<class 'numpy.ndarray'>
