Python, numpy sort array

Question

I'am using numpy and have an array (ndarray type) which contain some values. Shape of this array 1000x1500. I reshaped it

brr = np.reshape(arr, arr.shape[0]*arr.shape[1])

when I trying

brr.reverse()
AttributeError: ‘numpy.ndarray’ object has no attribute ‘reverse’

get error. How I can sort this array ?

Answer 1

If you just want to reverse it:

brr[:] = brr[::-1]

Actually, this reverses along axis 0. You could also revert on any other axis, if the array has more than one.

To sort in reverse order:

>>> arr = np.random.random((1000,1500))
>>> brr = np.reshape(arr, arr.shape[0]*arr.shape[1])
>>> brr.sort()
>>> brr = brr[::-1]
>>> brr
array([  9.99999960e-01,   9.99998167e-01,   9.99998114e-01, ...,
     3.79672182e-07,   3.23871190e-07,   8.34517810e-08])

or, using argsort:

>>> arr = np.random.random((1000,1500))
>>> brr = np.reshape(arr, arr.shape[0]*arr.shape[1])
>>> sort_indices = np.argsort(brr)[::-1]
>>> brr[:] = brr[sort_indices]
>>> brr
array([  9.99999849e-01,   9.99998950e-01,   9.99998762e-01, ...,
         1.16993050e-06,   1.68760770e-07,   6.58422260e-08])

Answer 2

Try this for sorting in descending order ,

import numpy as np
a = np.array([1,3,4,5,6])
print -np.sort(-a)

Answer 3

To sort a 1d array in descending order, pass reverse=True to sorted . As @Erik pointed out, sorted will first make a copy of the list and then sort it in reverse.

import numpy as np
import random
x = np.arange(0, 10)
x_sorted_reverse = sorted(x, reverse=True)