Shuffle a numpy array
I think this is very important to note.
You can use random.shuffle(a)
if a
is 1-D numpy array.
If it is N-D (where N > 2) than
random.shuffle(a)
will spoil your data and return some random thing. As you can see here:
import random
import numpy as np
a=np.arange(9).reshape((3,3))
random.shuffle(a)
print a
[[0 1 2]
[3 4 5]
[3 4 5]]
This is a known bug (or feature?) of numpy.
So, use only numpy.random.shuffle(a)
for numpy arrays.
You could shuffle a.flat
:
>>> np.random.shuffle(a.flat)
>>> a
array([[6, 1, 2],
[3, 5, 0],
[7, 8, 4]])
You can tell np.random.shuffle
to act on the flattened version:
>>> a = np.arange(9).reshape((3,3))
>>> a
array([[0, 1, 2],
[3, 4, 5],
[6, 7, 8]])
>>> np.random.shuffle(a.flat)
>>> a
array([[3, 5, 8],
[7, 6, 2],
[1, 4, 0]])