review random generator

[clach04]

• Py 3.6 >= https://docs.python.org/3/library/secrets.html#module-secrets - secrets.token_bytes()

• https://www.pycryptodome.org/src/random/random#Crypto.Random.get_random_bytes

• see other personal code that uses alternative system random (os.urandom)

  try:
      from secrets import choice, randbelow  # Python 3.6 module
  except ImportError:
      import random as _py_random
      random = _py_random  # backup(, backup) plan
  
  # Potentially overkill, use system random numbers
  # Nested exception catching for older Python version
  try:
      try:
          random = _py_random.SystemRandom()
      except NotImplementedError:
          # not available
          pass
  except AttributeError:
      # Pre Python 2.4
      pass
  
  def randbelow(x):
      return random.randint(0, x)
  choice = random.choice
  

For completeness, (Linux) should not be needed:

try:
    urandom = os.urandom
except AttributeError:
    if os.path.exists('/dev/urandom'):
        def urandom(n):
            # UNIX ONLY
            f = open('/dev/urandom')
            result = f.read(n)
            f.close()
            return result
    else:
        def urandom(n):
           s = []
           for i in xrange(n):
              r = random.randint(0,255)
              s.append(chr(r))
           return ''.join(s)

Windows only:

win32prng.getRandomBytes