Generating random number list in Python

There is a need to generate random numbers when studying a model or behavior of a program for different range of values. Python can generate such random numbers by using the random module. In the below examples we will first see how to generate a single random number and then extend it to generate a list of random numbers.

Generating a Single Random Number

The random() method in random module generates a float number between 0 and 1.

Example

import random

n = random.random()
print(n)

Output

Running the above code gives us the following result ?

0.2112200

Generating Number in a Range

The randint() method generates an integer between a given range of numbers (inclusive).

Example

import random

n = random.randint(0, 22)
print(n)

Output

Running the above code gives us the following result ?

2

Using For Loop

We can use the above randint() method along with a for loop to generate a list of numbers. We first create an empty list and then append the random numbers generated to the empty list one by one.

Example

import random

numbers = []
for i in range(0, 5):
    n = random.randint(1, 30)
    numbers.append(n)
print(numbers)

Output

Running the above code gives us the following result ?

[10, 5, 21, 1, 17]

Using random.sample()

We can also use the sample() method available in random module to directly generate a list of random numbers. Here we specify a range and give how many random numbers we need to generate. Note that sample() generates unique numbers without replacement.

Example

import random

# Generate 5 random numbers between 10 and 30
numbers = random.sample(range(10, 30), 5)
print(numbers)

Output

Running the above code gives us the following result ?

[16, 19, 13, 18, 15]

Using List Comprehension

A more Pythonic way to generate random number lists is using list comprehension with randint().

Example

import random

# Generate 5 random numbers between 1 and 100
numbers = [random.randint(1, 100) for _ in range(5)]
print(numbers)

Output

Running the above code gives us the following result ?

[45, 23, 78, 12, 56]

Comparison of Methods

Conclusion

Use random.sample() for unique numbers, list comprehension for concise syntax, or for loops for step-by-step control. Choose the method based on whether you need duplicates and your coding style preference.