How does Python generate random numbers?

Python includes a built-in package i.e random module for generating random numbers.

In this article, we will show you how to generate random numbers in python using different methods −

• Using random.seed() method

• Using random.randrange() method

• Using random.randint() method

• Using random.random()

• Using random.choice() method

• Using random.uniform() method

Method 1: Using random.seed() method

The random number generator is initialized using the seed() method.

To generate a random number, the random number generator requires a starting numeric value (a seed value).

NOTE − The random number generator utilizes the current system time by default.

To change the random number generator's starting number, use the seed() method.

You will get the same random number if you use the same seed value twice.

Syntax

random.seed(x, version)

Parameters

x(optional) − The seed value required to generate a random number. If it is an integer, it is utilized directly; otherwise, it must be converted to an integer.

version − An integer that specifies how to convert the ‘x’ argument to an integer. The default value is 2. The generator uses the current system time if the value is None.

The following program returns a random element from the list using random.random() and seed() methods −

import random
# Setting the seed value to 5
random.seed(5)
print(random.random())

# Setting the same seed value as above i.e 5
random.seed(5)
print(random.random())

Output

On executing, the above program will generate the following output −

0.62290169489
0.62290169489

We set the seed value to 5 and then used the random() function of the random module to generate a random value. Then we set the seed value to 5 again and used the random() function to generate the same random value as before. This is how the seed() function is used.

Method 2: Using random.randrange() method

The randrange() method selects an element at random from the specified range and returns it.

Syntax

random.randrange(start, stop, step)

Parameters

start(optional) − An integer indicating the starting position. 0 is the default

stop(required) − An integer indicating the end position.

step(optional) − It is an integer indicating the incrementation. 1 by default.

The following program returns the random number between the given range using the randrange() function −

import random

# generating a random number between 10(included) and 20(not included)
print("Random Number Generated = ", random.randrange(10, 20))

Output

On executing, the above program will generate the following output −

Random Number Generated = 13

The randrange() function is used here to generate a random number from a range. We passed the starting value (lower limit) and ending value (upper limit) as arguments, and it generated a random number between those ranges

Method 3: Using random.randint() method

The randint() method returns an integer value representing a randomly chosen element from the given range.

NOTE − The randint() method is an alias for randrange(start, stop+1).

Syntax

random.randint(start, stop)

Parameters

start(required) − An integer indicating the starting position.

stop(required) − An integer indicating the end position.

The following program returns the random number between the given range using the randint() function−

import random
# generating a random number between 10 and 20(both 10 and 20 numbers included)
print("Random Number Generated = ", random.randint(10, 20))

Output

On executing, the above program will generate the following output −

Random Number Generated = 20  

The difference between randrange() and randint is that randint includes the upper limit in the range, whereas randrange() excludes the upper limit. We can add a step value to the randrange() function but not to the randint() function.

Method 4: Using random.random()

The random() method generates a random floating-point value between 0 and 1.

Syntax

random.random()

Parameters

This random() method doesn’t accept any arguments

The following program returns the random number between the given range using the random() function −

import random
# generating a random floating-point number between 0 and 1
print("Random Number Generated = ", random.random())

Output

Random Number Generated = 0.15685132230226662

Method 5: Using random.choice() method

The choices() method returns a list containing the element from the provided sequence that was chosen at random.

The sequence could be a string, a range, a list, a tuple, or anything else.

The following program returns the random number from the list −

import random

#Input list
given_List = [ 1, 6, 3, 9, 10, 24, 475, 483, 2656]
print('The first Random Element from the list:',random.choice(given_List))
print('The Second Random Element from the list:',random.choice(given_List))

Output

The first Random Element from the list: 6
The Second Random Element from the list: 24

Method 6: Using random.uniform() method

The uniform() method generates a random floating number between the two input values (both numbers included).

Syntax

random.uniform(x, y)

Parameters

x(required) − number representing the lowest possible outcome

y(required) − number representing the highest possible outcome

The following program returns the random floating number between the given range using the uniform() function −

import random
# generating a random number between 10 and 20(both 10 and 20 are also included)
print("Random Number Generated = ", random.uniform(10, 20))

Output

Random Number Generated = 12.845596876772472

In this case, the uniform() function is used to generate a random floating number from a range. We gave it the starting (lower limit) and ending (upper limit) values as arguments, and it generated a random float/decimal number between those two ranges.

Conclusion

We learned how to generate a random number using six different methods in this article:

seed(),randrange(),randint(),choice(),random(),uniform() . We also learned how to use the choice() function to get a random element from a list/string/tuple.