randrange() in Python

Generating a random number has always been an important application and having many uses in daily life. Python offers a function that can generate random numbers from a specified range and also allowing rooms for steps to be included, called randrange() in random module. More to this function is discussed in this article.

Syntax : 
random.randrange(start(opt),stop,step(opt))
Parameters :
start(opt) :  Number consideration for generation starts from this,
default value is 0. This parameter is optional.
stop : Numbers less than this are generated. This parameter is mandatory.
step(opt) : Step point of range, this won't be included. This is optional.
Default value is 1.
Return Value : 
This function generated the numbers in the sequence start-stop skipping step.
Exceptions :
Raises ValueError if stop <= start and number is non- integral.

Python3

# Python code to demonstrate the working of
# randrange()

import random

# Using randrange() to generate numbers from 0-100
print ("Random number from 0-100 is : ",end="")
print (random.randrange(100))

# Using randrange() to generate numbers from 50-100
print ("Random number from 50-100 is : ",end="")
print (random.randrange(50,100))

# Using randrange() to generate numbers from 50-100
# skipping 5
print ("Random number from 50-100 skip 5 is : ",end="")
print (random.randrange(50,100,5))

Output: 

Random number from 0-100 is : 26
Random number from 50-100 is : 58
Random number from 50-100 skip 5 is : 90

Exceptions

1. Value Error – Floating point value 

Python3

# Python code to demonstrate the Exception of
# randrange(), ValueError, Float value

import random

# Using randrange() to generate numbers from 14.5-100
# Raises Exception
print ("Random number from 14.5-100 is : ",end="")
print (random.randrange(14.5,100))

Output : 

Random number from 14.5-100 is : 

Runtime Error : 

Traceback (most recent call last):
  File "/home/5e40f42505a6926d0c75a09bec1279d9.py", line 9, in 
    print (random.randrange(14.5,100))
  File "/usr/lib/python3.5/random.py", line 182, in randrange
    raise ValueError("non-integer arg 1 for randrange()")
ValueError: non-integer arg 1 for randrange()

2. Value Error – start >= stop 

Python3

# Python code to demonstrate the Exception of
# randrange(), ValueError, start >= start

import random

# Using randrange() to generate numbers from 500-100
# Raises Exception
print ("Random number from 500-100 is : ",end="")
print (random.randrange(500,100))

Output : 

Random number from 500-100 is : 

Runtime Error : 

Traceback (most recent call last):
  File "/home/ea327cf3f1dd801a66a185d101c5cb13.py", line 9, in 
    print (random.randrange(500,100))
  File "/usr/lib/python3.5/random.py", line 196, in randrange
    raise ValueError("empty range for randrange() (%d,%d, %d)" % (istart, istop, width))
ValueError: empty range for randrange() (500,100, -400)

Practical Application

Generating random numbers has always been an important application and has been used in many casino games, for gambling for many kid games like ludo, etc which use the concept of Dice. A short game, on who reaches 100 first wins have been depicted in the code below. Each player is allowed a dice of 1-10 numbers, i.e at each turn 1-10 can be attained..

Python3

# Python code to demonstrate the Application of
# randrange()

import random

sum = 0
sum1 = 0
count = 0
flag = 0

while(1):

    # generate random number at each turn 1-10
    r1 = random.randrange(1,10)
    r2 = random.randrange(1,10)

    # adding to account of players
    sum = sum + r1
    sum1 = sum1 + r2
    count = count+1

    print ("Total score of Player 1 after turn %d is :  %d " % (count,sum))

    # break when player 1 reaches 100
    if(sum>=100):
      flag=1
      break
    print ("Total score of Player 2 after turn %d is :  %d" % (count,sum1))

    # break when player 2 reaches 100
    if(sum1>=100):
      flag=2
      break

if(flag==1):
   print("\nPlayer 1 wins the game")
else :
   print("\nPlayer 2 wins the game")

Output

Total score of Player 1 after turn 1 is :  8 
Total score of Player 2 after turn 1 is :  4
Total score of Player 1 after turn 2 is :  13 
Total score of Player 2 after turn 2 is :  8
Total score of Player 1 after turn 3 is :  22 
Total score of Player 2 after turn 3 is :  16
Total score of Player 1 after turn 4 is :  28 
Total score of Player 2 after turn 4 is :  22
Total score of Player 1 after turn 5 is :  33 
Total score of Player 2 after turn 5 is :  27
Total score of Player 1 after turn 6 is :  35 
Total score of Player 2 after turn 6 is :  33
Total score of Player 1 after turn 7 is :  36 
Total score of Player 2 after turn 7 is :  42
Total score of Player 1 after turn 8 is :  38 
Total score of Player 2 after turn 8 is :  50
Total score of Player 1 after turn 9 is :  45 
Total score of Player 2 after turn 9 is :  55
Total score of Player 1 after turn 10 is :  48 
Total score of Player 2 after turn 10 is :  61
Total score of Player 1 after turn 11 is :  54 
Total score of Player 2 after turn 11 is :  64
Total score of Player 1 after turn 12 is :  57 
Total score of Player 2 after turn 12 is :  70
Total score of Player 1 after turn 13 is :  66 
Total score of Player 2 after turn 13 is :  73
Total score of Player 1 after turn 14 is :  72 
Total score of Player 2 after turn 14 is :  75
Total score of Player 1 after turn 15 is :  79 
Total score of Player 2 after turn 15 is :  76
Total score of Player 1 after turn 16 is :  81 
Total score of Player 2 after turn 16 is :  77
Total score of Player 1 after turn 17 is :  89 
Total score of Player 2 after turn 17 is :  81
Total score of Player 1 after turn 18 is :  95 
Total score of Player 2 after turn 18 is :  90
Total score of Player 1 after turn 19 is :  97 
Total score of Player 2 after turn 19 is :  99
Total score of Player 1 after turn 20 is :  102 

Player 1 wins the game

This article is contributed by Manjeet Singh. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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