字符串的numpy数组 [英] numpy array of chars to string

问题描述

我有一个2D numpy char数组(来自NetCDF4文件)，它实际上表示一个字符串列表.我想将其转换为字符串列表.

I have a 2D numpy char array (from a NetCDF4 file) which actually represents a list of strings. I want to convert it into a list of strings.

我知道我可以使用join()将字符连接成一个字符串，但是我只能找到一种方法一次处理一个字符串:

I know I can use join() to concatenate the chars into a string, but I can only find a way to do this one string at a time:

data = np.array([['a','b'],['c','d']])
for row in data[:]:
    print ''.join(row)

但是它非常慢.如何在单个命令中返回字符串数组?谢谢

But it's very slow. How can I return an array of strings in a single command? Thanks

推荐答案

列表理解是最"pythonic"的方式.

The list comprehension is the most "pythonic" way.

最"numpythonic"的方式是:

The most "numpythonic" way would be:

>>> data = np.array([['a','b'],['c','d']])
# a 2D view
>>> data.view('S2')
array([['ab'],
       ['cd']], 
      dtype='|S2')
# or maybe a 1D view ...fastest solution:
>>> data.view('S2').ravel()
array(['ab', 'cd'], 
      dtype='|S2')

没有循环，没有列表理解，甚至没有副本.缓冲区只是保持不变，并带有不同的视图"，因此这是最快的解决方案.

No looping, no list comprehension, not even a copy. The buffer just sits there unchanged with a different "view" so this is the fastest solution available.

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