Generate Random Float numbers in Python using random() and Uniform() functions

In this article, I will show you how to generate a random float number in Python. Also, we will learn how to use random.random() and random.uniform() functions of a random module.

Goals of this lesson. In this lesson, you’ll learn how to:

• Generate a random float number between 0 and 1
• Generate a random float number between a float range
• Generate a random float number up to 2 decimal places
• Generate a list of random floats in Python
• Get a secure random float number
• Use a NumPy’s random package to generate an array of random float numbers.

random.random() to generate a random floating-point number between 0 to 1

In this example, we will see how to generate a random float number between 0 to 1 using random.random() function. This function generates a random float number uniformly in the semi-open range [0.0, 1.0).

import random

x = random.random()
print("Random float number is ", x)
print("Random float number is ", random.random())

Output:

Printing random float number  0.8504482249878023
Printing random float number  0.5769147269189085

Note: A random.random() function can only provide float numbers between 0.1. to 1.0. To generate a random float number between any two numbers, we can use random.uniform()

random.uniform() to get a random float number within a range

The random.uniform() function returns a random floating-point number between a given range in Python. Let’s assume you want to generate a random float number between 10 to 100 Or from 50.50 to 75.5. In such cases, you should use random.uniform() function.

Syntax of random.uniform()

random.uniform(start, stop)

The random.uniform() function returns a random floating-point number N such that start <= N <= stop.

Arguments

• The random.uniform function accepts two arguments and both the arguments are compulsory.
• If you miss any of them, you will get a TypeError: uniform() missing 1 required positional argument.

In simple words, random.uniform(10.5, 20.5) will generate any float number which is greater than or equal to 10.5 and less than or equal to the 20.5.

Examples to get a random float number between float range

Let see how to use the random.uniform() function to get a random float number within a range.

import random

x = random.uniform(10.5, 100.5)
print("Random float number between range 10.5 to 100.5 ", x)

print("Random float number between 10 and 100 is ", random.uniform(10, 100))
print("Random float number between 25.5 and 250 is ", random.uniform(25.5, 250))
print("Random float number between 250 and 25.5 is ", random.uniform(250, 25.5))

Output:

Random float number between range 10.5 to 100.5  81.53168715590648
Random float number between 10 and 100 is  14.63784738314109
Random float number between 25.5 and 250 is  216.9180052775547
Random float number between 250 and 25.5 is  184.21261638366832

Points to remember about random.uniform()

The start value need not be smaller than the stop value.

• If start <= stop the random.uniform() function generates a random float number which is greater than or equal to the start number and less than or equal to the stop number.
• If  stop <= start the random.uniform() function generates a random float number which is greater than or equal to the stop number and less than or equal to the start number.
• For example, you can generate a random float number between 10 to 100 and also from 100 to 10. Both treated the same.

The step argument is not available in random.uniform()

Generate a random float number up to 2 decimal places

As you can see in the above examples, generated a random float number has more than ten decimal places. In many cases, we need a random float number with limited decimal digits after the decimal point. Let’s see how to get a random float number with 2 decimal places.

You can use the round() function with the random.random() and random.uniform() function to limit float number precision to two decimal places.

import random

print("Random float number with 2 decimal places")
num2 = round(random.random(), 2)
print(num2)

num2 = round(random.uniform(33.33, 66.66), 2)
print(num2)

print("Random float number with 1 decimal places")
print(round(random.random(), 1))
print(round(random.uniform(33.33, 66.66), 1))

Output:

Random float number with 2 decimal places
0.66
54.99
Random float number with 1 decimal places
0.9
43.2

Get random Decimal

The random.uniform() and random.random() only returns float number. To get a random decimal.Decimal instance, you need explicitly convert it into decimal.Decimal.

import random
import decimal

# random decimal
x = decimal.Decimal(str(random.uniform(100, 1000)))
print(x)

Output:

936.3682817788443

How to get a random float number from the range()

How to generate a random float number from a range() with a specific interval (The step value)?

For example, If you want to get a random integer from a range(1, 100, 2) with an interval 2, you can do that easily using random.choice(range(1, 100, 2)). But as you know, range() doesn’t support the float numbers. In this case, we need to convert an integer to floats.

import random

# random float from 1 to 99.9
int_num = random.choice(range(10, 1000))
float_num = int_num/10
print(float_num)

Output: 81.2

Generate a list of random floats between a range

In this section, we will see how to generate multiple random float numbers. In this example, we will see how to create a list of 10 random floats within a range of 50.50 to 500.50.

import random

# list of random float between a range 50.50 to 500.50
randomFloatList = []
# Set a length of the list to 10
for i in range(0, 10):
    # any random float between 50.50 to 500.50
    # don't use round() if you need number as it is
    x = round(random.uniform(50.50, 500.50), 2)
    randomFloatList.append(x)

print("Printing list of 10 random float numbers")
print(randomFloatList)

Output:

Printing list of 10 random float numbers
[104.26, 212.3, 238.17, 120.05, 160.21, 269.71, 362.45, 360.05, 311.65, 329.72]

Note: In the above example, there is a chance to get duplicate float numbers in a list. let’s see how to generate a list of unique random floats.

Create a list of unique random float numbers

If you want to generate a list of unique random integers, you can do that easily using random.sample(range(1, 100), 10)). The random.sample() never generates the duplicate. But as you know, range() doesn’t support the float numbers. But we have two workarounds to get the list of unique random float numbers. Let’s see those.

Option 1: Use a list of integers to generate floats

import random

list_Size = 10
# random float from 1 to 99.9
integer_list = random.sample(range(10, 1000), list_Size)
float_list = [x/10 for x in integer_list]
print(float_list)

Output:

[7.9, 84.6, 72.1, 92.9, 64.1, 2.8, 32.6, 36.9, 97.4, 64.4]

Option 2: Avoid duplicates manually

import random

def get_float_list(start, stop, size):
    result = []
    unique_set = set()
    for i in range(size):
        x = round(random.uniform(start, stop),2)
        while x in unique_set:
            x = round(random.uniform(start, stop),2)
        unique_set.add(x)
        result.append(x)

    return result

print("List of unique random numbers between 100, 1000")
print(get_float_list(100, 1000, 10))

Output:

List of unique random numbers between 100, 1000
[918.45, 544.86, 595.18, 830.98, 516.11, 531.88, 255.85, 727.47, 687.23, 558.28]

Difference between random.uniform() and random.random()

• The random.random() function takes no parameters while random.uniform() takes two parameters, i.e., start and stop.
• The random.random() function generates a random float number between 0.0 to 1.0, but never return upper bound. I.e., It will never generate 1.0. On the other side random.uniform(start, stop) generates a random float number between the start and stop number. Due to the rounding effect, it can return a stop number.

Generate a secure random float number

Above all examples are not cryptographically secure. The cryptographically secure random generator generates random numbers using synchronization methods to ensure that no two processes can obtain the same number at the same time. If you are producing random floats for a security-sensitive application, then you must use this approach.

Use the random.SystemRandom().random()  or random.SystemRandom().uniform() functions to generate a secure random float number in Python.

Example

import random

print("Secure random float numbers are")
secure_random = random.SystemRandom()

randomfloat = secure_random.random()
print(randomfloat)

randomfloat = secure_random.uniform(12.5, 77.5)
print(randomfloat)

Output:

Secure random float numbers are 
0.800760229291861
35.0470859352744

Use Numpy.random to generate an array of random float numbers

NumPy isn’t a part of a standard Python library. However, it has various functions to generate random data. You can install NumPy using pip install numpy. Let see how to use it to generate a random float number and create an array of random float numbers.

Get random float number using a NumPy

import numpy

random_float = numpy.random.randn()
print(random_float)

Output:

0.833280610141848

Generate a random float number between any float range using NumPy

import numpy

random_float_number = numpy.random.uniform(49.5, 99.5)
print(random_float_number)

Output:

59.11713060647423

Create an n-dimensional array of float numbers using NumPy

Use a numpy.random.rand() to create an n-dimensional array of float numbers and populate it with random samples from a uniform distribution over [0, 1).

import numpy

random_float_array = numpy.random.rand(2, 3)
print("Random float array 2X3 \n")
print(random_float_array,"\n")

Output:

Random float array 2X3

[[0.34344184 0.8833125  0.76322675]
 [0.17844326 0.7717775  0.86237081]]

Create an n-dimensional array of float numbers between any float range.

Here we will use Use a numpy.random.uniform() function to generate a random 2×2 array.

import numpy

#2X2 random float
random_float_array = numpy.random.uniform(75.5, 125.5, size=(2, 2))
print(random_float_array)

Output:

[[107.50697835 123.84889979]
[106.26566127 101.92179508]] 

So What Do You Think?

I want to hear from you. Do you know other alternative ways of generating random float numbers Python? Or I missed one of the usages of random.uniform()?. Either way, let me know by leaving a comment below.

Also, try to solve the following exercise and quiz to have a better understanding of working with random data in Python.