Question

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

Answer 1

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).