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So, I need a code for school where I need to generate 4 random numbers using randint and they can't be duplicates, I just cant seem to get my head around it. - Cheers

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  • Hint: How would you do it with dice? Commented Jun 10, 2017 at 23:28
  • 3
    Throw a dice. If its number is equal to any of the other dice, throw it again. Commented Jun 10, 2017 at 23:33
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    @PM2Ring Well I think part of the OP's problem was that he was trying to over-complicate things. Maybe if you would have added a bit more to your hint stating not to over-think things, he might have got it. Commented Jun 10, 2017 at 23:43
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    @Lewis: No reason to feel stupid here. We all have made some mistakes that are not obvious to us at the time but become clear down the road. Commented Jun 10, 2017 at 23:45
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    Thanks Mountain Tech :) Just getting started, know the basics moving on to slightly more advanced now. Commented Jun 10, 2017 at 23:50

2 Answers 2

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Use random.sample to randomly select 4 elements from a list.

import random
low, high = 0, 1000
w, x, y, z = random.sample(range(low, high) , 4)

Set low and high to your desired range from where you want to sample numbers.

Here's a less wasteful solution using randint (sorry for not seeing this earlier), if you want to generate any number in a wide range.

numbers = set()
while len(numbers) < 4:
    num = random.randint(low, high)
    if num not in numbers:
        numbers.add(num)

w, x, y, z = numbers
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3 Comments

@Lewis Try my second one and tell me how it goes.
Thanks coldspeed :)
@Lewis Cheers mate.
3

We can accomplish a list of 4 random numbers by using a while loop to create a random number then append that number to a list only if that number does not already exist in the list. If we can append list then x -= 1 until x == 0 then the while loop will stop and the code will print out the list.

It will be different every time.

import random

x = 4
list_of_random_numbers = []
while x != 0:
    new_random_number = random.randint(0,999) # you can define any range of numbers here.
    if new_random_number not in list_of_random_numbers:
        list_of_random_numbers.append(new_random_number)
        x -= 1

print (list_of_random_numbers)

Edit:

Also as PM 2Ring said you can just check the length of the list as well:

import random

list_of_random_numbers = []
while len(list_of_random_numbers) < 4:
    new_random_number = random.randint(0,999) # you can define any range of numbers here.
    if new_random_number not in list_of_random_numbers:
        list_of_random_numbers.append(new_random_number)

print (list_of_random_numbers)
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12 Comments

Thank you! Works like a charm! :)
You might as well just check the length of the list rather than maintaining x to track the count. All of Python's standard collection types store their current length as an attribute, so calling len on them is very efficient. Using a list here is probably no slower than using a set (checking set membership is O(1), but checking list membership is O(n) because it requires a linear scan), but for larger collections, using a set will be faster.
@PM 2Ring: LoL... I was thinking the opposite for some reason... Been a long day.
@Lewis: No worries. Always accept the answer that is best for you. If you like other answers as well you can always upvote late :)
@SierraMountainTech Congrats on 1k!
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