Numpy random number

[Bryant]

I am a beginner of Python. And I am a bit confused by different way of generating random numbers. Appreciate if anyone can explain the difference below:

import numpy as np
a1 = np.random.random((1,4))
a2 = np.random.random(4)

Thank you!

[MTVDNA]

The difference is in the output: a2 returns an array of 4 floats, whereas a1 returns a 1x4 multidimensional array of floats, the first dimension in this case being 1.

If you print the output you'll get something like this:

import numpy as np
a1 = np.random.random((1,4))
a2 = np.random.random(4)

print("a1:", a1)
print("a2:", a2)

Output:
a1: [[ 0.59946856  0.98460562  0.2970344   0.93185208]]
a2: [ 0.84642216  0.76289462  0.02371878  0.48856006]

See the difference? The way you can access the values is different of course:

# first value of first array in a1
r1= a1[0][0]
# first value of a2
r2 = a2[0]

You can add as many dimensions as you like:

# make a 2 x 4 multidimensional array of random floats
a3 = np.random.random((2,4))
print(a3)
print("")
# make a 2 x 3 x 4 multidimensional array of random floats
a4 = np.random.random((2,3,4))
print(a4)

Output:
[[ 0.24597847  0.31471039  0.66878251  0.12768539]
 [ 0.82398123  0.97512768  0.39540696  0.43854987]]

[[[ 0.27224315  0.77992856  0.54579919  0.24076665]
  [ 0.56690179  0.2984007   0.4736477   0.45876745]
  [ 0.31631711  0.8529202   0.10593129  0.44203135]]

 [[ 0.47631484  0.76030139  0.31148261  0.81140939]
  [ 0.71954076  0.98883936  0.97953863  0.01995996]
  [ 0.54762994  0.73041063  0.8126263   0.11215006]]]

If you are not sure how a certain function works, you can just google the name: numpy.random.random and you'll find the documentation:
https://docs.scipy.org/doc/numpy/referen...andom.html