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Random Numbers in Python

  • Difficulty Level : Easy
  • Last Updated : 21 Jan, 2021

Python defines a set of functions that are used to generate or manipulate random numbers through the random module. Functions in the random module rely on a pseudo-random number generator function random(), which generates a random float number between 0.0 and 1.0. These particular type of functions is used in a lot of games, lotteries, or any application requiring a random number generation.

Random Number Operations

1. choice() :- choice() is an inbuilt function in the Python programming language that returns a random item from a list, tuple, or string.

Example:

Python3




# Python3 program to demonstrate the use of
# choice() method
 
# import random
import random
 
# prints a random value from the list
list1 = [1, 2, 3, 4, 5, 6]
print(random.choice(list1))
 
# prints a random item from the string
string = "striver"
print(random.choice(string))

Output:

5
t

2. randrange(beg, end, step):- The random module offers a function that can generate random numbers from a specified range and also allowing rooms for steps to be included, called randrange().



Example:

Python




# Python code to demonstrate the working of
# choice() and randrange()
 
# importing "random" for random operations
import random
 
# using choice() to generate a random number from a
# given list of numbers.
print("A random number from list is : ", end="")
print(random.choice([1, 4, 8, 10, 3]))
 
# using randrange() to generate in range from 20
# to 50. The last parameter 3 is step size to skip
# three numbers when selecting.
print("A random number from range is : ", end="")
print(random.randrange(20, 50, 3))

Output: 

A random number from list is : 4
A random number from range is : 41

3. random():- This method is used to generate a float random number less than 1 and greater or equal to 0.

4. seed():- Seed function is used to save the state of a random function so that it can generate some random numbers on multiple executions of the code on the same machine or on different machines (for a specific seed value). The seed value is the previous value number generated by the generator. For the first time when there is no previous value, it uses current system time.

Example:

Python




# Python code to demonstrate the working of
# random() and seed()
 
# importing "random" for random operations
import random
 
# using random() to generate a random number
# between 0 and 1
print("A random number between 0 and 1 is : ", end="")
print(random.random())
 
# using seed() to seed a random number
random.seed(5)
 
# printing mapped random number
print("The mapped random number with 5 is : ", end="")
print(random.random())
 
# using seed() to seed different random number
random.seed(7)
 
# printing mapped random number
print("The mapped random number with 7 is : ", end="")
print(random.random())
 
# using seed() to seed to 5 again
random.seed(5)
 
# printing mapped random number
print("The mapped random number with 5 is : ", end="")
print(random.random())
 
# using seed() to seed to 7 again
random.seed(7)
 
# printing mapped random number
print("The mapped random number with 7 is : ", end="")
print(random.random())

Output: 

A random number between 0 and 1 is : 0.510721762520941

The mapped random number with 5 is : 0.6229016948897019



The mapped random number with 7 is : 0.32383276483316237

The mapped random number with 5 is : 0.6229016948897019

The mapped random number with 7 is : 0.32383276483316237

5. shuffle():- It is used to shuffle a sequence (list). Shuffling means changing the position of the elements of the sequence. Here, the shuffling operation is in place.

Example:

Python3




# import the random module
import random
 
 
# declare a list
sample_list = ['A', 'B', 'C', 'D', 'E']
 
print("Original list : ")
print(sample_list)
 
# first shuffle
random.shuffle(sample_list)
print("\nAfter the first shuffle : ")
print(sample_list)
 
# second shuffle
random.shuffle(sample_list)
print("\nAfter the second shuffle : ")
print(sample_list)

Output:

Original list : 
['A', 'B', 'C', 'D', 'E']

After the first shuffle : 
['A', 'B', 'E', 'C', 'D']

After the second shuffle : 
['C', 'E', 'B', 'D', 'A']

6. uniform(a, b):- This function is used to generate a floating point random number between the numbers mentioned in its arguments. It takes two arguments, lower limit(included in generation) and upper limit(not included in generation).
 

Python




# Python code to demonstrate the working of
# shuffle() and uniform()
 
# importing "random" for random operations
import random
 
# Initializing list
li = [1, 4, 5, 10, 2]
 
# Printing list before shuffling
print("The list before shuffling is : ", end="")
for i in range(0, len(li)):
    print(li[i], end=" ")
print("\r")
 
# using shuffle() to shuffle the list
random.shuffle(li)
 
# Printing list after shuffling
print("The list after shuffling is : ", end="")
for i in range(0, len(li)):
    print(li[i], end=" ")
print("\r")
 
# using uniform() to generate random floating number in range
# prints number between 5 and 10
print("The random floating point number between 5 and 10 is : ", end="")
print(random.uniform(5, 10))

Output: 

The list before shuffling is : 1 4 5 10 2 

The list after shuffling is : 2 1 4 5 10 

The random floating point number between 5 and 10 is : 5.183697823553464

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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