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annotate roundup/anypy/random_.py @ 5488:52cb53eedf77

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reworked random number use prefer secrets module from Python 3.6+, random.SystemRandom and finally plain random
author Christof Meerwald <cmeerw@cmeerw.org>
date Sat, 04 Aug 2018 22:40:16 +0100
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children adf54478cdaf
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5488
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1 try:
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2 from secrets import choice, randbelow, token_bytes
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3 def seed(v = None):
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4 pass
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5
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6 is_weak = False
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7 except ImportError:
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8 import os as _os
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9 import random as _random
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10
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11 # prefer to use SystemRandom if it is available
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12 if hasattr(_random, 'SystemRandom'):
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13 def seed(v = None):
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14 pass
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15
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16 _r = _random.SystemRandom()
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17 is_weak = False
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18 else:
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19 # don't completely throw away the existing state, but add some
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20 # more random state to the existing state
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21 def seed(v = None):
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22 import os, time
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23 _r.seed((_r.getstate(),
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24 v,
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25 hasattr(os, 'getpid') and os.getpid(),
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26 time.time()))
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27
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28 # create our own instance so we don't mess with the global
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29 # random number generator
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30 _r = _random.Random()
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31 seed()
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32 is_weak = True
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33
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34 choice = _r.choice
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35
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36 def randbelow(i):
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37 return _r.randint(0, i - 1)
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38
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39 if hasattr(_os, 'urandom'):
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40 def token_bytes(l):
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41 return _os.urandom(l)
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42 else:
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43 def token_bytes(l):
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44 _bchr = chr if str == bytes else lambda x: bytes((x,))
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45 return b''.join([_bchr(_r.getrandbits(8)) for i in range(l)])
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