Random number generator with conditions - Python

user_13643429 0
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I am new to Python and trying to generate 5 numbers with 2 conditions:

  1. There must be 3 even and 2 odd numbers
  2. From those 5 numbers 3 must be low (1,51) and 2 high (51,100). Which number will be low or high is not of interest.

I have managed to solve the first part:

import random
rand_even = random.sample(range(0, 100, 2), 3)
rand_odd = random.sample(range(1, 100, 2), 2)
rand_total = rand_even,rand_odd
print(rand_total)

Obviously this is not getting me anywhere For the second part i thought i could use something like:

rand_low = random.sample(range(0, 51), 3)
rand_high = random.sample(range(51,100), 2)

But obviously this is not the way as i am getting more than 5 numbers.

Any help would be appriciated. Thank you

python
4 Answers

The question is, as pointed out by others, whether we allow correlations between the numbers being high/low and even/odd. The following code does not introduce this correlation.

import random
n = 5                                                                           
odd = 2                                                                         
high = 2                                                                        

odd_indices = random.sample(range(n), odd)                                      
high_indices = random.sample(range(n), high)                                    
out = random.sample(range(26),n)                                                
for i in range(n):                                                              
    out[i] *= 2                                                                 
    if i in odd_indices:                                                        
        out[i] += 1                                                             
    if i in high_indices:                                                       
        out[i] += 50

Please note that this includes the number 100 as output option. Strictly speaking you did not include it, so one could introduce a shift if the 100 is hit:

    if out[i]==100:
        out[i] -= random.sample(range(1,25),1)[0]*2

This code is not optimized for performance.

edit

This code will have an irregularity, though, as in each possible output 2k and 2k+1 never occur at the same time for any k.

user_134891150

I tried working through this problem logically and it got pretty messy.

Heuristically, what about something like this:

def valid_list(l):
    evens, odds = 0, 0
    lows, highs = 0, 0
    for elem in l:
        if elem%2 == 0:
            evens += 1
        else:
            odds += 1
        if elem < 52:
            lows += 1
        else:
            highs += 1
    return evens <= 3 and odds <= 2 and lows <= 3 and highs <= 2

current_list = [random.randint(0, 100)]

while len(current_list) < 5:
    if not valid_list(current_list):
        current_list[-1] = random.randint(0, 100)
    else:
        current_list.append(random.randint(0, 100))

print(current_list)

You have a function that constantly checks whether the numbers you have so far are on track/valid, and then a while loop that will keep pegging said function with random numbers until there is a list of 5 numbers that pass valid_list.

This is pretty much the epitome of randomness, haha

user_86529200

If you don't care which numbers are high/low or even/odd, you can just say that the high numbers are even (since you need 3 low, and 3 even numbers).

This code just gives 3 low even numbers, and 2 high odd numbers:

import random
rand_even_low = random.sample(range(0, 52, 2), 3)
rand_odd_high = random.sample(range(51, 1000, 2), 2)
rand_total = rand_even_low + rand_odd_high
print(rand_total)
user_136420430 
from random import seed
from random import random
import math
odd=0
even=0
below_50=0
above_50=0
numbers=[]
#Providing seed value to random()
seed(2)
while len(numbers)<5:
    num=math.floor(random()*100)
    #checking to maintain unique elements
    if num not in numbers:
        if num%2==0 and even<3:
            if num>50 and above_50<2:
                even+=1
                above_50+=1
                numbers.append(num)
            elif num<50 and below_50<3:
                even+=1
                below_50+=1
                numbers.append(num)
        elif num%2==1 and odd<2:
            if num>50 and above_50<2:
                odd+=1
                above_50+=1
                numbers.append(num)
            elif num<50 and below_50<3:
                odd+=1
                below_50+=1
                numbers.append(num)
user_84221700
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