Generate n unique random numbers within a range

Question

I know how to generate a random number within a range in Python   random randint numLow  numHigh    And I know I can put this in a loop to generate n amount of these numbers  for x in range  0  n       listOfNumbers append random randint numLow  numHigh     However  I need to make sure each number in that list is unique  Other than a load of conditional statements  is there a straightforward way of generating n number of unique random numbers   The important thing is that each number in the list is different to the others    So   12  5  6  1    good  But   12  5  5  1    bad  because the number 5 occurs twice

User · Accepted Answer

If you just need sampling without replacement:

>>> import random
>>> random.sample(range(1, 100), 3)
[77, 52, 45]

random.sample takes a population and a sample size k and returns k random members of the population.

If you have to control for the case where k is larger than len(population), you need to be prepared to catch a ValueError:

>>> try:
...   random.sample(range(1, 2), 3)
... except ValueError:
...   print('Sample size exceeded population size.')
... 
Sample size exceeded population size

User · Answer

Generate the range of data first and then shuffle it like this  import random data   range numLow  numHigh  random shuffle data  print data   By doing this way  you will get all the numbers in the particular range but in a random order   But you can use random sample to get the number of elements you need  from a range of numbers like this  print random sample range numLow  numHigh   3

User · Answer

You could use the random sample function from the standard library to select k elements from a population   import random random sample range low  high   n    In case of a rather large range of possible numbers  you could use itertools islice with an infinite random generator   import itertools import random  def random gen low  high       while True          yield random randrange low  high   gen   random gen 1  100  items   list itertools islice gen  10      Take first 10 random elements   After the question update it is now clear that you need n distinct  unique  numbers   import itertools import random  def random gen low  high       while True          yield random randrange low  high   gen   random gen 1  100   items   set      Try to add elem to set until set length is less than 10 for x in itertools takewhile lambda x  len items   lt  10  gen       items add x

User · Answer

You could add to a set until you reach n   setOfNumbers   set   while len setOfNumbers   lt  n      setOfNumbers add random randint numLow  numHigh     Be careful of having a smaller range than will fit in n  It will loop forever  unable to find new numbers to insert up to n

[python] Generate 'n' unique random numbers within a range

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