Creating a list of random numbers without duplicates in python

Question

so what I am trying to do is create a list of 5 numbers for the game mastermind, and I would like to eliminate all duplicates! The issue is that the code sometimes creates a list with 3 numbers, or 4, or sometimes 5, it seems to be random.

I should also mention we are not allowed to be usin grandom.sample, or random.shuffle

import random

def generatePassword() :
    lis = []
    for i in range(5) :
        #This checks to see if there are duplicate numbers
        r = random.randint(1,9)
        if r not in lis :
            lis.append(r)
        i+=1
    return lis



def main() :
    print(generatePassword())
main()

Answer 1

Use numpy.random.permutation if you are looking for method that works and is faster:

import numpy as np
your_list = list(np.random.permutation(np.arange(0,10))[:5])

>>> your_list
[6, 9, 0, 1, 4]

Alternatively, you can use np.random.choice with replace=False :

your_list = list(np.random.choice(np.arange(0,10), 5, replace=False)

Answer 2

Try using a while loop with a condition that checks for the length of lis

while len(lis) < 5:

instead of your for loop

Answer 3

The function random.sample does what you want:

import random

def generatePassword():
    numbers = range(0, 9)
    return random.sample(numbers, 5)

def main() :
    print(generatePassword())
main()

Answer 4

I do not recommend the solution in this answer - the best option in the standard library is probably random.sample , and there may be more efficient methods using numpy. Both of these options are suggested in other answers.

---

This method uses random.shuffle to shuffle a list of digits, then selects the first five. This avoids the issue of a theoretically unbounded loop ( while len(nums) < 5: ), but does not scale well when the range of numbers to choose from (here, 1 to 9) is significantly larger than how many numbers are needed (here, 5).

import random

population = list(range(1, 10))
random.shuffle(population)
print(population[:5])

Answer 5

You don't want to add random, unique integers 5 times; you want to add random, unique integers until your list contains 5 elements. This'll do it:

import random

def generatePassword() :
    lis = []
    while len(lis) < 5:
        #This checks to see if there are duplicate numbers
        r = random.randint(1,9)
        if r not in lis :
            lis.append(r)
    return lis

Answer 6

So your problem: It won't add the same number twice. But since you use a for i in range(5): it will only repeat 5 times, regardless of if it added a unique number or not.

You need to measure the length of the list, so it will always add 5 random, unique numbers to the list.

You have the code mostly right, but all you need to do is replace: for i in range(5): with: while len(lis) < 5:

Make sure to delete the i += 1 though. It will cause an error if you don't.

Here's the code:

import random

def generatePassword() :
    lis = []
    while len(lis) < 5:
        #This checks to see if there are duplicate numbers
        r = random.randint(1,9)
        if r not in lis :
            lis.append(r)
    return lis



def main() :
    print(generatePassword())
main()