如何在numpy中创建字符数组？ [英] How do I create character arrays in numpy?

问题描述

说我有以下数组：

  import numpy as np 
a = ['hello'，'snake '，'plate'] 
  

我想把它变成一个numpy数组 b 以便：

  b [0,0] ='h'
b [ 0,1] ='e'
b [0,2] ='l'
b [1,0] ='s'
 ... 
  
 
 
 
我想让标准的numpy技巧工作，比如广播，比较等。
 
 
 
如何做？ 
 
 
 
 $ r 
 $ b 
 
解决方案
您可以直接创建numpy字符数组，例如：
  b'='n'，'a'，'k'，'e' ]，['p'，'l'，'a'，'t'，'e']] 
  
 
 $ b 
 
 
 
如果你有 a ，并希望请注意：
  list（'hello'）== ['h' e'，'l'，'l'，'o'] 
  
 ：
  b = np.array（a中的单词列表（word））
  
但是，如果 a 有不等长的单词（例如 ['snakes'，'on'，'a'，'plane'] ），你想用较短的词语做什么？您可以用空格将其填充最长的字词：
  wid = max（len（w）for w in a）
b = np.array（[list（w.center（wid））for w in a]）
  
其中 string.center（width）用空格填充，以字符串为中心。您也可以使用 rjust 或 ljust （请参阅 string docs ）。
 
Say I have the following array:
import numpy as np
a = ['hello','snake','plate']
I want this to turn into a numpy array b so that:
b[0,0] = 'h'
b[0,1] = 'e'
b[0,2] = 'l'
b[1,0] = 's'
...
I want the standard numpy tricks to work, like broadcasting, comparison, etc.

How is it done?  And where is this in the numpy documentation?

Thanks!

Uri
解决方案
You can create a numpy character array directly e.g.:
b = np.array([ ['h','e','l','l','o'],['s','n','a','k','e'],['p','l','a','t','e'] ])
The usual array tricks work with this.

If you have a and wish to generate b from it, note that:
list('hello') == ['h','e','l','l','o']
So you can do something like:
b = np.array([ list(word) for word in a ])
However, if a has words of unequal length (e.g. ['snakes','on','a','plane']), what do you want to do with the shorter words? You could pad them with spaces to the longest word:
wid = max(len(w) for w in a)
b = np.array([ list(w.center(wid)) for w in a])
Which the string.center(width) pads with spaces, centering the string. You could also use rjust or ljust (see string docs).

                        
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