How to generate random numbers by a certain step?-CodePudding

For school we have to create a program in python in which we generate a given number of random numbers and you can choose by what multiplication. I tried this code (which will show my list is empty) but I'm wondering if there is a specific function for this in python because I cant seem to find out how to do it.

Also, we can't use any other function than randint()

from random import randint

list = []
aantal = int(input("Hoeveel random getallen wilt u? "))
veelvoud = int(input("Welke veelvoud? "))

for i in range(aantal):
    getal = randint(1, 100)
    if getal % veelvoud == 0:
        list.append(getal)
    else:
        i -= 1

print(list)

CodePudding user response：

You can use random.randrange. For example

random.randrange(5, 101, 5)

will give a random number in {5, …, 95, 100}.

If you want several of them, the best way is a list comprehension. So

[random.randrange(multiple, 101, multiple) for _ in range(count)]

will give you a list of count numbers 1–100 inclusive, requiring that they be multiples of multiple.

So your code can be

from random import randrange

aantal = int(input("Hoeveel random getallen wilt u? "))
veelvoud = int(input("Welke veelvoud? "))

print([randrange(veelvoud, 101, veelvoud) for _ in range(aantal)])

Note that your original code would not give aantal numbers, because your i -= 1 does not do anything in this context – the for loop overwrites the value of i on every iteration.

CodePudding user response：

Here's a different way to approach the problem:

Request user input for the number of random numbers, and the step
Create an empty list
While the list contains less elements than the number requested, generate random numbers between 1 and 100
Check if the random number is a multiple of the step, and if so, add it to the list

from random import randint

number = int(input("How many random numbers to generate?: "))
step = int(input("Multiple of which number? : "))

nums_list = []

while len(nums_list) < number:
  rand = randint(1, 100)
  if rand % step != 0:
    continue
  else:
    nums.append(rand)

print(nums_list)

An even more efficient way would be to generate random numbers in a way such that the number will always be a multiple of the step:

from random import randint

number = int(input("How many random numbers to generate?: "))
step = int(input("Multiple of which number? : "))

# The highest number that can be multiplied with the step to
# produce a multiple of the step less than 100
max_rand = floor(100/step)

nums_list = []

for _ in range(number):
  rand = randint(1, max_rand) * step
  nums_list.append(rand)

print(nums_list)

CodePudding user response：

I did a bit of research and I think this is the easiest and most used/known method. You can bring a bit more randomness into it when you multiply two random numbers but idk, seems weird to me.