I would like to generate random numbers in the range (0..."MAX"). I would like to make a loop such that every time going through the loop a new unique random number is generated (should not repeat). The loop will continue a total of "MAX" times. There should be "MAX" number of random numbers generated in total. When sorted, the values should be 0..."MAX"; no repetition.
Restrictions: - Assume MAX is much larger than int. (no memory to store all number permutations in memory)
My proposed solution: If I seed the generator from 0...MAX would that allow me to print every unique number between 0 and MAX as in the below function? Assume there's no space to store all numbers and shuffling them.
for x in range (0, MAX):
random.seed(x)
num=random.randint(0, MAX)
print("seed = ",x, " random number = ", num)
If the answer for the above is yes then would this generation be reversible (can i get the seed from the random number)? In which case would this be considered a kind of block cipher that is if the seed (key) and the range is the same length?
You can do like this:
input = set()
for i in range(MAX):
input.add(random.randrange(x,y))
print input
with in the range of x and y it will select some random values. W/o repetition means you can use set. so i am adding those values to set.
just make a try this one.
The random module has a sample function , which is predicated on producing unique elements
. It is used as in the following example:
random_list = random.sample(xrange(10000000), 60)
# generates a list of 60 random numbers in the
# range 0 to 10000000 without repetition
But, do be aware that it will throw an exception if the length of the list is greater than the size of the population, eg
random_list = random.sample(xrange(5), 60 # you will get a ValueError here
If you want to get all the numbers within a particular range,
either we have to store the generated random numbers and compare them against the newly generated random number
import random result = [] # hash values of numbers between -5 to 256 are the same as the # numbers themselves. So, whatever may be the order, set will have them # in the sorted order. So, `result` cannot be a `set` here. for x in range (0, 10): num = random.randint(0, 10) while num in result: num = random.randint(0, 10) result.append(num) print result
or we can generate the list and shuffle it like this
data = range(10) import random random.shuffle(data) print data
since you already have the population as a list and random.shuffle
is an in-place operation, the result doesn't have to be stored in a separate list.
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