Create random list of integers in Python

Question

I d like to create a random list of integers for testing purposes  The distribution of the numbers is not important  The only thing that is counting is time  I know generating random numbers is a time-consuming task  but there must be a better way  Here s my current solution  import random import timeit    Random lists from  0-999  interval print  random randint 0  1000  for r in xrange 10     v1 print  random choice  i for i in xrange 1000    for r in xrange 10     v2    Measurement  t1   timeit Timer   random randint 0  1000  for r in xrange 10000      import random     v1 t2   timeit Timer  random sample range 1000   10000     import random     v2  print t1 timeit 1000  1000 print t2 timeit 1000  1000  v2 is faster than v1  but it is not working on such a large scale  It gives the following error   ValueError  sample larger than population  Is there a fast  efficient solution that works at that scale  Some results from the answer Andrew s  0 000290962934494 gnibbler s  0 0058455221653 KennyTM s  0 00219276118279 NumPy came  saw  and conquered

User · Accepted Answer

It is not entirely clear what you want  but I would use numpy random randint   import numpy random as nprnd import timeit  t1   timeit Timer   random randint 0  1000  for r in xrange 10000      import random     v1      Change v2 so that it picks numbers in  0  10000  and thus runs    t2   timeit Timer  random sample range 10000   10000     import random     v2 t3   timeit Timer  nprnd randint 1000  size 10000     import numpy random as nprnd     v3  print t1 timeit 1000  1000 print t2 timeit 1000  1000 print t3 timeit 1000  1000   which gives on my machine   0 0233682730198 0 00781716918945 0 000147947072983   Note that randint is very different from random sample  in order for it to work in your case I had to change the 1 000 to 10 000 as one of the commentators pointed out -- if you really want them from 0 to 1 000 you could divide by 10    And if you really don t care what distribution you are getting then it is possible that you either don t understand your problem very well  or random numbers -- with apologies if that sounds rude

User · Answer

Your question about performance is moot   both functions are very fast  The speed of your code will be determined by what you do with the random numbers   However it s important you understand the difference in behaviour of those two functions  One does random sampling with replacement  the other does random sampling without replacement

User · Answer

Firstly  you should use randrange 0 1000  or randint 0 999   not randint 0 1000   The upper limit of randint is inclusive   For efficiently  randint is simply a wrapper of randrange which calls random  so you should just use random  Also  use xrange as the argument to sample  not range   You could use   a for a in sample xrange 1000  1000  for   in range 10000 1000     to generate 10 000 numbers in the range using sample 10 times    Of course this won t beat NumPy      python2 7 -m timeit -s  from random import randrange    randrange 1000  for   in xrange 10000    10 loops  best of 3  26 1 msec per loop    python2 7 -m timeit -s  from random import sample    a 1000 for a in sample xrange 10000  10000    100 loops  best of 3  18 4 msec per loop    python2 7 -m timeit -s  from random import random    int 1000 random    for   in xrange 10000     100 loops  best of 3  9 24 msec per loop    python2 7 -m timeit -s  from random import sample    a for a in sample xrange 1000  1000  for   in range 10000 1000    100 loops  best of 3  3 79 msec per loop    python2 7 -m timeit -s  from random import shuffle  gt  def samplefull x    gt    a   range x   gt    shuffle a   gt    return a    a for a in samplefull 1000  for   in xrange 10000 1000    100 loops  best of 3  3 16 msec per loop    python2 7 -m timeit -s  from numpy random import randint   randint 1000  size 10000   1000 loops  best of 3  363 usec per loop     But since you don t care about the distribution of numbers  why not just use   range 1000   10000 1000

User · Answer

All the random methods end up calling random random   so the best way is to call it directly    int 1000 random random    for i in xrange 10000     For example    random randint calls random randrange  random randrange has a bunch of overhead to check the range before returning istart   istep int self random     n     NumPy is much faster still of course

[python] Create random list of integers in Python

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