Question

0

I want to write a data string to a numpy array. Pseudo Code:

d=numpy.zeros(10,dtype=numpy.character)
d[1:6]='hello'

Example result:

d=
  array(['', 'h', 'e', 'l', 'l', 'o', '', '', '', ''],
        dtype='|S1')

How can this be done with numpy most naturally and efficiently? I don't want for loops, generators, or anything iterative, can it be done with one command as with the pseudo code?

edited Nov 18 at 22:19

asked Nov 18 at 21:29

user213060
316●9

29% accept rate

Paul · Answer 1 · 2009-11-18 21:33:32Z

1

Just explicitly make your text a list (rather than that it is iterable from Python) and Numpy will understand it automatically:

>>> text = 'hello'
>>> offset = 1
>>> d[offset:offset+len(text)] = list(text)
>>> d

array(['', 'h', 'e', 'l', 'l', 'o', '', '', '', ''],
      dtype='|S1')

answered Nov 18 at 21:33

Paul
628●10

	Ugly and not in-place, but does work. Thanks. – user213060 Nov 18 at 22:22
	I tried using an iter to avoid the memory overhead for huge strings. You will not believe what numpy did --- d[1:6]=iter('hello') – user213060 Nov 18 at 22:26
	omg, that's why I told you to use a list in the first place... – Paul Nov 18 at 22:38

musicinmybrain · Answer 2 · 2009-11-24 12:47:40Z

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There's little need to build a list when you have numpy.fromstring and numpy.fromiter.

answered Nov 24 at 12:47

musicinmybrain
151●4

I'm writing many strings to different positions on the same array. – user213060 Nov 25 at 15:08

bpowah · Answer 3 · 2009-12-12 18:00:14Z

0

What you might want to try is python's array type. It will not have as high an overhead as a list.

from array import array as pyarray
d[1:6] = pyarray('c', 'hello')

answered Dec 12 at 18:00

bpowah
1,180●2●9

Write a data string to a numpy character array?

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