Shuffle an array with python randomize array item order with python

Question

What s the easiest way to shuffle an array with python

User · Answer

Be aware that random shuffle   should not be used on multi-dimensional arrays as it causes repetitions    Imagine you want to shuffle an array along its first dimension  we can create the following test example   import numpy as np x   np zeros  10  2  3    for i in range 10      x i         i np ones  2 3     so that along the first axis  the i-th element corresponds to a 2x3 matrix where all the elements are equal to i   If we use the correct shuffle function for multi-dimensional arrays  i e  np random shuffle x   the array will be shuffled along the first axis as desired  However  using random shuffle x  will cause repetitions  You can check this by running len np unique x   after shuffling which gives you 10  as expected  with np random shuffle   but only around 5 when using random shuffle

User · Answer

Alternative way to do this using sklearn  from sklearn utils import shuffle X  1 2 3  y     one    two    three   X  y   shuffle X  y  random state 0  print X  print y    Output    2  1  3    two    one    three     Advantage  You can random multiple arrays simultaneously without disrupting the mapping  And  random state  can control the shuffling for reproducible behavior

User · Answer

import random random shuffle array

User · Answer

I don t know I used random shuffle   but it return  None  to me  so I wrote this  might helpful to someone  def shuffle arr       for n in range len arr  - 1           rnd   random randint 0   len arr  - 1           val1   arr rnd          val2   arr rnd - 1           arr rnd - 1    val1         arr rnd    val2      return arr

User · Answer

When dealing with regular Python lists  random shuffle   will do the job just as the previous answers show   But when it come to ndarray numpy array   random shuffle seems to break the original ndarray  Here is an example   import random import numpy as np import numpy random  a   np array  1 2 3 4 5 6   a shape    3 2  print a random shuffle a    a will definitely be destroyed print a   Just use  np random shuffle a   Like random shuffle  np random shuffle shuffles the array in-place

User · Answer

import random random shuffle array

User · Answer

You can sort your array with random key  sorted array  key   lambda x  random random      key only be read once so comparing item during sort still efficient   but look like random shuffle array  will be faster since it written in C

User · Answer

The other answers are the easiest  however it s a bit annoying that the random shuffle method doesn t actually return anything - it just sorts the given list   If you want to chain calls or just be able to declare a shuffled array in one line you can do       import random     def my shuffle array           random shuffle array          return array   Then you can do lines like       for suit in my shuffle   hearts    spades    clubs    diamonds

User · Answer

Be aware that random shuffle   should not be used on multi-dimensional arrays as it causes repetitions    Imagine you want to shuffle an array along its first dimension  we can create the following test example   import numpy as np x   np zeros  10  2  3    for i in range 10      x i         i np ones  2 3     so that along the first axis  the i-th element corresponds to a 2x3 matrix where all the elements are equal to i   If we use the correct shuffle function for multi-dimensional arrays  i e  np random shuffle x   the array will be shuffled along the first axis as desired  However  using random shuffle x  will cause repetitions  You can check this by running len np unique x   after shuffling which gives you 10  as expected  with np random shuffle   but only around 5 when using random shuffle

User · Answer

import random random shuffle array

User · Answer

import random random shuffle array

User · Answer

The other answers are the easiest  however it s a bit annoying that the random shuffle method doesn t actually return anything - it just sorts the given list   If you want to chain calls or just be able to declare a shuffled array in one line you can do       import random     def my shuffle array           random shuffle array          return array   Then you can do lines like       for suit in my shuffle   hearts    spades    clubs    diamonds

User · Answer

arr   numpy array to shuffle  def shuffle arr       a   numpy arange len arr       b   numpy empty 1      for i in range len arr            sel   numpy random random integers 0  high len a -1  size 1          b   numpy append b  a sel           a   numpy delete a  sel      b   b 1   astype int      return arr b

User · Answer

import random random shuffle array

User · Answer

Alternative way to do this using sklearn  from sklearn utils import shuffle X  1 2 3  y     one    two    three   X  y   shuffle X  y  random state 0  print X  print y    Output    2  1  3    two    one    three     Advantage  You can random multiple arrays simultaneously without disrupting the mapping  And  random state  can control the shuffling for reproducible behavior

User · Answer

import random random shuffle array

User · Answer

Just in case you want a new array you can use sample   import random new array   random sample  array  len array

User · Answer

You can sort your array with random key  sorted array  key   lambda x  random random      key only be read once so comparing item during sort still efficient   but look like random shuffle array  will be faster since it written in C

User · Answer

import random random shuffle array

User · Answer

When dealing with regular Python lists  random shuffle   will do the job just as the previous answers show   But when it come to ndarray numpy array   random shuffle seems to break the original ndarray  Here is an example   import random import numpy as np import numpy random  a   np array  1 2 3 4 5 6   a shape    3 2  print a random shuffle a    a will definitely be destroyed print a   Just use  np random shuffle a   Like random shuffle  np random shuffle shuffles the array in-place

User · Answer

import random random shuffle array

User · Answer

In addition to the previous replies  I would like to introduce another function   numpy random shuffle as well as random shuffle perform in-place shuffling  However  if you want to return a shuffled array numpy random permutation is the function to use

User · Answer

Just in case you want a new array you can use sample   import random new array   random sample  array  len array

User · Answer

arr   numpy array to shuffle  def shuffle arr       a   numpy arange len arr       b   numpy empty 1      for i in range len arr            sel   numpy random random integers 0  high len a -1  size 1          b   numpy append b  a sel           a   numpy delete a  sel      b   b 1   astype int      return arr b

User · Answer

I don t know I used random shuffle   but it return  None  to me  so I wrote this  might helpful to someone  def shuffle arr       for n in range len arr  - 1           rnd   random randint 0   len arr  - 1           val1   arr rnd          val2   arr rnd - 1           arr rnd - 1    val1         arr rnd    val2      return arr

User · Answer

In addition to the previous replies  I would like to introduce another function   numpy random shuffle as well as random shuffle perform in-place shuffling  However  if you want to return a shuffled array numpy random permutation is the function to use

[python] Shuffle an array with python, randomize array item order with python

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