Random Numbers in NumPy
What is a Random Number?
Random number does NOT mean a different number every time. Random means something that cannot 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 somealgorithm to generate a random number as well.
If there is a program to generate random number it can bepredicted, thus it is not truly random.
Random numbers generated through a generation algorithm are calledpseudo 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 someoutside source. This outside source is generally our keystrokes, mouse movements, data on networketc.
We do not need truly random numbers, unless it is related to security (e.g. encryption keys) or the basis ofapplication is the randomness (e.g. Digital roulette wheels).
In this tutorial we will be using pseudo random numbers.
Generate Random Number
NumPy offers therandom module to work with random numbers.
Example
Generate a random integer from 0 to 100:
x = random.randint(100)
print(x)
Generate Random Float
The random module'srand() method returns a random float between 0 and 1.
Example
Generate a random float from 0 to 1:
x = random.rand()
print(x)
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
Therandint() method takes asizeparameter where you can specify the shape of an array.
Example
Generate a 1-D array containing 5 random integers from 0 to 100:
x=random.randint(100, size=(5))
print(x)
Example
Generate a 2-D array with 3 rows, each row containing 5 random integers from 0 to 100:
x = random.randint(100, size=(3, 5))
print(x)
Floats
Therand() method also allows you to specify the shape of the array.
Example
Generate a 1-D array containing 5 random floats:
x = random.rand(5)
print(x)
Example
Generate a 2-D array with 3 rows, each row containing 5 random numbers:
x = random.rand(3, 5)
print(x)
Generate Random Number From Array
Thechoice() method allows you to generate a random value based on an array of values.
Thechoice() method takes an array as a parameter and randomly returns one of the values.
Example
Return one of the values in an array:
x = random.choice([3, 5, 7, 9])
print(x)
Thechoice() method also allows you to return anarray of values.
Add asize 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):
x = random.choice([3, 5, 7, 9], size=(3, 5))
print(x)
