What is a Random Number?
Random number does NOT mean a different number every time. Random means something that can not be predicted logically.
Pseudo Random and True Random.
Computers work on programs, and programs are definitive set of instructions. So it means there must be some algorithm to generate a random number as well.
If there is a program to generate random number it can be predicted, thus it is not truly random.
Random numbers generated through a generation algorithm are called pseudo random.
Can we make truly random numbers?
Yes. In order to generate a truly random number on our computers we need to get the random data from some outside source. This outside source is generally our keystrokes, mouse movements, data on network etc.
We do not need truly random numbers, unless its related to security [e.g. encryption keys] or the basis of application is the randomness [e.g. Digital roulette wheels].
In this tutorial we will be using pseudo random numbers.
Generate Random Number
NumPy offers the random module to work with random numbers.
Example
Generate a random integer from 0 to 100:
from numpy import random
x = random.randint[100]
print[x]
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Generate Random Float
The random module's rand[] method returns a random float between 0 and 1.
Example
Generate a random float from 0 to 1:
from numpy import random
x = random.rand[]
print[x]
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Generate Random Array
In NumPy we work with arrays, and you can use the two methods from the above examples to make random arrays.
Integers
The randint[] method takes a size parameter where you can specify the shape of an array.
Example
Generate a 1-D array containing 5 random integers from 0 to 100:
from numpy import random
x=random.randint[100, size=[5]]
print[x]
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Example
Generate a 2-D array with 3 rows, each row containing 5 random integers from 0 to 100:
from numpy import random
x = random.randint[100, size=[3, 5]]
print[x]
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Floats
The rand[] method also allows you to specify the shape of the array.
Example
Generate a 1-D array containing 5 random floats:
from numpy import random
x = random.rand[5]
print[x]
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Example
Generate a 2-D array with 3 rows, each row containing 5 random numbers:
from numpy import random
x = random.rand[3, 5]
print[x]
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Generate Random Number From Array
The choice[] method allows you to generate a random value based on an array of values.
The choice[] method takes an array as a parameter and randomly returns one of the values.
Example
Return one of the values in an array:
from numpy import random
x = random.choice[[3, 5, 7, 9]]
print[x]
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The choice[] method also allows you to return an array of values.
Add a size parameter to specify the shape of the array.
Example
Generate a 2-D array that consists of the values in the array parameter [3, 5, 7, and 9]:
from numpy import random
x = random.choice[[3, 5, 7, 9], size=[3, 5]]
print[x]
Try it Yourself »
In this article, we show how to create an array of random integers in Python with Numpy.
To create an array of random integers in Python with numpy, we use the random.randint[] function.
Into this random.randint[] function, we specify the range of numbers that we want that the random integers can be selected from and how many integers we want.
In the code below, we select 5 random integers from the range of 1 to 100.
So, first, we must import numpy as np.
We then create a variable named randnums and set it equal to, np.random.randint[1,101,5]
This produces an array of 5 numbers in which we can select from integers 1 to 100.
1 is inclusive and 101 is exclusive, so the possible integers that we can select from is 1 to 100.
We then display the contents of randnums, which is a random array of 5 integers.
We'll now show one more example.
We're going to create an array of 10 integers that can select from integers to 1-25.
This is shown in the code below.
So now you see an array of 10 random integers.
However, random arrays are not confined to single-dimensional arrays. Arrays can also be multidimensional.
To create random multidimensional arrays, we specify a size attribute and that tells us the size of the array.
For example, if we want an array of 4x5 [4 rows and 5 columns], we specify size= [4,5].
Below is the code to create a random 4 x 5 array in Python.
So this is how you can generate random multidimensional arrays in Python.
And this is all that is required to create an array of random integers in Python with numpy.
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