How to Generate Random Numbers in Python?

In Data Science or Statistics, there are various instances where a programmer might need to work with random inputs. Python offers many predefined functions to generate and use random data.

In this article, we will guide you on how to generate random numbers of int and float types using Python. We will particularly focus on the random library in Python. So, without further ado, let’s get started! 

We will be covering the following sections today: 

• Methods to Generate Random Numbers in Python  
• Generating a floating random number between 0 and 1 – random() 
• Generating a random integer within a given range – randint() 
• Generating a random integer list using for loop – randint() 
• Generating a sample of random integers within a given range – sample() 
• Selecting a random number from a given list – choice() 
• Generating a random number from a list in the specified range – randrange() 
• Generating a floating random number within a given range – uniform() 
• Generating a randomly shuffled list – shuffle() 
• Generating a floating random number sequence – seed() 

Methods to Generate Random Numbers in Python  

The random module in Python contains pseudo-random number generators for various distributions: 

Let’s see how each of the above methods works to generate random numbers: 

Generating a floating random number between 0 and 1 – random() 

One method is to use the random() function, from the random module, that generates a random float value in the range [0.0, 1.0], as shown: 

Output:

What have we done here?  

• We first import the random module of Python. 
• Then, we call the random() method to get a random float between 0-1 and store it in the variable n. 
• Print the randomly generated number. 

Generating a random integer within a given range – randint() 

The random module also provides a randint() method to generate an integer number within a specified range.  Let’s understand how to generate random number in Python with Range.

The function takes two numbers as arguments, [min, max] – defining the lower and upper limit of the range. Let’s look at the following example: 

Output:

63

What have we done here?  

• Firstly, import the random module of Python. 
• Then, we call the randint(min, max) method to get a random integer within the given range and store it in the variable n. 
• Print the randomly generated number. 

Generating a random integer list using for loop – randint() 

We can also use the randint() method of the random module to generate a list of integer numbers. For this, we make use of for loop that iterates over a specified range.  

Let’s look at the following example: 

#Import the random library  
import random 
 
rand_list = []   
for i in range(0,5):   
    n = random.randint(100,200)   
    rand_list.append(n)   
print(rand_list) 

Output:

[199, 107, 199, 103, 112]

What have we done here?  

• Import the random module of Python. 
• Declare an empty Python list variable rand_list. 
• Then, use a for loop to iterate over a range that will determine the number of elements in the list.
• Once the loop has completed its execution, print the randomly generated number list. 

Generating a sample of random integers within a given range – sample() 

The random module also provides a sample() method to generate a sampled list of random numbers within a specified range.  

Let’s understand through the following example: 

#Import the random library  
import random 
 
n = random.sample(range(50,100), 10) 
print(n)

Output:

[58, 56, 64, 54, 84, 50, 80, 89, 87, 55]

What have we done here?  

• Import the random module of Python. 
• Then, we simply call the sample() function that takes range(min, max) as one argument, and the number of elements in the list as the other argument, which is 10 in this case. 
• Finally, we print the sample of 10 randomly generated numbers between 50-100. 

Selecting a random number from a given list – choice() 

The random module provides another in-built method called choice() that returns a random element from a list, tuple, or string.  

Let’s look at the following example: 

#Import the random library  
import random 
 
mylist = [1, 3, 5, 7, 9] 
 
#Print a random number from the list 
n = random.choice(mylist) 
print(n) 

Output:

3

What have we done here?  

• Import the random module of Python. 
• Declare a variable mylist and initialize it with the given elements: [1, 3, 5, 7, 9] 
• Then, we call the choice() function that takes the list variable as an argument and generates a random element from the specified list. 

Generating a random number from a list in the specified range – randrange() 

This random module method called the randrange() function, generates a random number from a list obtained by start-stop skipping within a specified range.  

The function takes three arguments, [start(optional),stop,step(optional)] – defining the start and stop of the range. There is also a step parameter that determines the step point of the range.  

Let’s understand through the following example: 

#Import the random library  
import random 
 
n = random.randrange(20, 50, 4) 
print(n)

Output:

44

What have we done here?  

• Import the random module of Python. 
• Then, we call the randrange() function, which takes the start=20, stop=50, and step=4 as parameters in this case. 
• The function generates a random element from the list [24,28,32,36,40,44,48] that is obtained from the specified range.  

Generating a floating random number within a given range – uniform() 

The random module also provides a uniform() method to generate a random floating-point value within a specified range.  

The function takes two numbers as arguments, [x,y] – defining the lower and upper limit of the range. Let’s look at the following example: 

#Import the random library  
import random 
 
n = random.uniform(13,17) 
print(n)   

Output:

14.821073447519757

What have we done here?  

• Import the random module of Python. 
• Then, call the uniform(x,y) function to get a random float value within the given range and store it in the variable n. 
• Print the randomly generated number. 

Generating a randomly shuffled list – shuffle() 

The random module has a shuffle() function that takes a Python list as an argument and shuffles the elements of the list in place to return None. 

Let’s understand through the following example: 

#Import the random library  
import random 
 
mylist = [1, 2, 3, 4, 5, 6, 7] 
 
#Print a random list 
random.shuffle(mylist) 
print(mylist) 
 
 

Output:

[3, 4, 5, 2, 1, 6, 7]

What have we done here?  

• Import the random module of Python. 
• Declare a variable mylist and initialize it with the given elements: [1,2,3,4,5,6,7] 
• Then, we call the shuffle() function that takes the list variable as an argument and generates a shuffled list with the same elements.  
• Print the list. 

Generating a floating random number sequence – seed() 

Lastly, the random module has a seed() function that can be used when you need to generate a sequence of random floating-point values. 

This function takes the seed value as an argument, which initializes the pseudo-random number generator. Let’s understand through the following example: 

#Import the random library  
import random 
 
#Specify seed 
val = int(input("Enter seed value : ")) 
 
random.seed(val) 
for i in range(val): 
    print(random.random(), end = ' ') 

Output:

What have we done here?  

• Import the random module of Python. 
• Take an integer input from the user as the seed value and store it in the variable val. 
• Then, call the seed() function with the input seed value as the argument. 
• Inside the function body, run a for loop iterating it over the range of the seed value. 
• Use the random() function to generate floating random numbers as specified by the seed value. For instance, in the above case, the given seed is 3, so a sequence of three floating-point values is printed. 

Endnotes 

In this article, we discussed the most common methods in Python’s random module that are capable of generating pseudo-random numbers. We learned how to generate random integers as well as random floating-point values. We also learned how to select random elements from a Python list. If you’d like to learn more about Python and practice Python programming, you can explore related articles here. 

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