Dice roller in Python (random.randint, face counts)

random.randint(1, 6) gives a whole number from 1 to 6, like one throw of a normal die. Call it once for each die and add the results.

The program

python

import random

random.seed(12)  # fixed seed so the output matches this page; remove it for real use


def roll_dice(count, sides=6):
    return [random.randint(1, sides) for _ in range(count)]


count = int(input("How many dice? "))
rolls = roll_dice(count)
print("You rolled:", rolls)
print("Total:", sum(rolls))

Typed in this example: 3. Press Run to type your own.

output

How many dice? 3
You rolled: [4, 3, 6]
Total: 13

How it works

random.randint(1, sides) includes both ends, so a six-sided die gives 1, 2, 3, 4, 5 or 6.
The list comprehension calls randint once for each die. _ is the usual name for a loop variable you do not use.
sides=6 is a default argument. roll_dice(2, sides=20) rolls two 20-sided dice.

Counting each face over many rolls

With a fair die, each face should come up about one time in six. Roll 6000 times and count:

python

import random

random.seed(12)  # fixed seed so the output matches this page; remove it for real use

rolls = 6000
counts = {face: 0 for face in range(1, 7)}

for _ in range(rolls):
    face = random.randint(1, 6)
    counts[face] += 1

for face, n in counts.items():
    percent = n / rolls * 100
    print(f"{face}: {n:4} ({percent:.1f}%)")

output

1:  994 (16.6%)
2: 1016 (16.9%)
3: 1037 (17.3%)
4:  982 (16.4%)
5:  992 (16.5%)
6:  979 (16.3%)

Each count is close to 1000 (16.7%), but not exactly 1000. Random results always vary a little. The more rolls you make, the closer the percentages get to 16.7%.

The dictionary starts with every face at 0. Without that, counts[face] += 1 would raise a KeyError the first time a face appears. The frequency table program shows other ways to count.

Two dice: why 7 comes up most

When you add two dice, the totals are not equally likely. There are six ways to make 7 (1+6, 2+5, 3+4, 4+3, 5+2, 6+1), but only one way to make 2 or 12:

python

import random

random.seed(12)  # fixed seed so the output matches this page; remove it for real use

counts = {total: 0 for total in range(2, 13)}
for _ in range(3600):
    counts[random.randint(1, 6) + random.randint(1, 6)] += 1

for total, n in counts.items():
    print(f"{total:2} {'#' * (n // 20)}")

output

 2 ####
 3 ##########
 4 ################
 5 ##################
 6 ########################
 7 #############################
 8 #########################
 9 #####################
10 ################
11 #########
12 ####

Each # stands for 20 rolls. The bars rise to a peak at 7 and fall again.