Generating random numbers in python

Question

I'm trying to make a basic dice roller. When i run this program in Codeskulptor, it throws an error on the randint function. Can I not set the range for it using raw_input plugged into variables? Is there a different function I should use?

"""Program to roll random numbers within the ranges set."""

import random
sides_of_die=raw_input("Enter how many sides your die has: ")
number_of_dice=raw_input("Enter number of dice you have: ")
total=sides_of_die*number_of_dice
rollinput=raw_input("Would you like to roll now?")
rollinputcap=rollinput.upper()
if rollinputcap =="Y":
    print random.randint(number_of_dice,total)
else:
    print "What do you want then?"

The distribution of multiple dice is not the same as the the distribution of sides*number, you need to get a random number for each die and add them if you want to be accurate. — Mark Ransom
– Mark Ransom, Commented Sep 15, 2013 at 1:34

TerryA · Accepted Answer · 2013-09-15 01:17:46Z

2

raw_input() returns a string, not an integer. To convert it to an integer type, use int():

sides_of_die = int(raw_input("Enter how many sides your die has: "))
number_of_dice = int(raw_input("Enter number of dice you have: "))

What's happening in your code is, you may input "6" and "2", so when you do total = sides_of_die * number_of_dice, you're getting a TypeError

answered Sep 15, 2013 at 1:17

TerryA

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AndyG · Accepted Answer · 2014-03-12 03:54:16Z

2

This is just because raw_input returns a string, not a number, while randint accept two numbers as arguments

so you should do

total = int(raw_input(..))

Point is, this is not always secure. Exceptions are very likely to be thrown, so you might want to use a try block; but for the time being, I think it's okay (I'm assuming you're just learning Python).

Another thing, which is rather important:

Look at the exception! If you'd read it, you would have known exactly what the problem was.

edited Mar 12, 2014 at 3:54

AndyG

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answered Sep 15, 2013 at 1:19

Ant

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CT Zhu · Accepted Answer · 2013-09-17 05:27:44Z

1

Beside the raw_input() problem pointed out by the others, @Mark Ransom's comment is important: the sum of dice value eventually follows normal distribution. See: http://en.wikipedia.org/wiki/Dice#Probability

Your:

if rollinputcap =="Y":
    print random.randint(number_of_dice,total)

should be changed to

if rollinputcap =="Y":
    sum_dice=[]
    for i in range(number_of_dice):
        sum_dice.append(random.randint(1, sides_of_dice))
    print sum(sum_dice)

edited Sep 17, 2013 at 5:27

answered Sep 15, 2013 at 1:52

CT Zhu

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1 Comment

Mark Ransom Over a year ago

You can shorten the summation considerably with a generator expression: sum(random.randint(1, sides_of_die) for n in range(number_of_dice))

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