How To Really Effectively Generate random numbers/strings

randGen.py

'''
Any Generator outputs an element x of type (Rational, Integer, Real, Complex, Character Set(s), any other type) from its Set X
s.t. x \subset X from a Given Set X or more.

So a pool of elements already given, from an academic point of view how is the RANDOMNESS in a function achieved?
'''
import random

def swap(minIndex, j, arr):
	'''Swap elements from two given positions'''
  arr[minIndex], arr[j] = arr[j], arr[minIndex]

def rangeRand (min, max):
    ''' Generates a random number between min and max excluding max
    There is a gap between two endpoint integers and that's the delta.
    The minimum number that generator can generator is the minima/lowest of the two endpoints,
    that's why you do (delta and generate a random Integer between 0 and 1) + minimum number'''
    return (random.random() * (max-min)) + min;

def shuffle (arr):
    '''in-place Shuffle from a given Set X; list of elements'''
    index=0
    ln = arr.length
    while (index<ln):
    	# ~O(N)
      #  to be truly uniformly random, min and max are least and present greatest value
    	index += 1
    	swap(rangeRand(0, index), index, arr)
    return arr;