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Python random.seed behaved strangely

I called random.seed (234), then called random.randint (0, 99) and got 92. When I repeated this process several times again, I got 86. When I called random.randint a second time, it returned 92. I expected the first value to be not 86, not 92. Why was it 92?

The following is the full output of the log. I included all of this in that there was some previous action that could explain the apparent erroneous behavior:

In [1]: import random

In [2]: import string

In [3]: string.letters
Out[3]: 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'

In [4]: string.ascii_letters
Out[4]: 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'

In [5]: string.printable
Out[5]: '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~ \t\n\r\x0b\x0c'

In [6]: len(string.printable)
Out[6]: 100

In [7]: [string.printable[random.randint(0,99)] for i in range(20)]
Out[7]: 
['{',
'+',
'[',
'\r',
'R',
'Z',
'v',
'|',
'v',
'e',
'T',
'x',
'\\',
'}',
'0',
'>',
'V',
'\n',
'`',
'`']

In [8]: ''.join([string.printable[random.randint(0,99)] for i in range(20)])
Out[8]: '%Z\\%mx4Z53uUZIa5KHe*'

In [9]: ''.join([string.printable[random.randint(0,99)] for i in range(20)])
Out[9]: 'Fg\nDHW+oV?-9``}\x0by%xD'

In [10]: import os

In [11]: os.urandom(1)
Out[11]: '('

In [12]: os.urandom(1)
Out[12]: '8'

In [13]: os.urandom(1)
Out[13]: '\xb1'

In [14]: os.urandom(1)
Out[14]: ')'

In [15]: os.urandom(1)
Out[15]: '\x8c'

In [16]: os.urandom(1)
Out[16]: '^'

In [17]: os.urandom(1)
Out[17]: '{'

In [18]: os.urandom(1)
Out[18]: '\x8f'

In [19]: ''.join(os.urandom(10))
Out[19]: '{t\x8dR\x1d\x83\xef\xd6N\xbd'

In [20]: ''.join(os.urandom(10))
Out[20]: '\x96\\\xf6\xe3\xf4/\x1f\xc7\x90\x02'

In [21]: from random import SystemRandom

In [22]: crypt = SystemRandom()

In [23]: ''.join([string.printable[crypt.randrange(100)] for i in range(20)])
Out[23]: "WoDVH\r1!?1+djB'f<;nW"

In [24]: ''.join([string.printable[crypt.randrange(100)] for i in range(20)])
Out[24]: '\rf?zo`7^{Y_Zx^[SYw7c'

In [25]: ''.join([string.printable[crypt.randrange(100)] for i in range(20)])
Out[25]: "3k*uGVIP'~^{P*~bserk"

In [26]: ''.join([string.printable[crypt.randrange(100)] for i in range(20)])
Out[26]: '~lkM/a&#_F&D\n<sC&i\r\n'

In [27]: random.seed(234)

In [28]: random.randint(0,99)
Out[28]: 92

In [29]: random.seed(234)

In [30]: random.randint(0,99)
Out[30]: 86

In [31]: random.seed(234)

In [32]: random.randint(0,99)
Out[32]: 86

In [33]: random.seed(234)

In [34]: random.randint(0,99)
Out[34]: 86

In [35]: random.randint(0,99)
Out[35]: 92

In [36]: random.randint(0,99)
Out[36]: 48

In [37]: random.seed(234)

In [38]: random.randint(0,99)
Out[38]: 86

In [39]: import sys

In [40]: sys.version_info
Out[40]: sys.version_info(major=2, minor=7, micro=13, releaselevel='final', serial=0)

In [41]: sys.version
Out[41]: '2.7.13 (default, Dec 17 2016, 23:03:43) \n[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)]'

** change, strange: repeating the "same" seemingly erroneous behavior ** In the same terminal window, I closed the previous ipython session. I did some action on the command line, then opened ipython again. I have done several different jobs. Then I tried again:

In [37]: import random

In [38]: random.seed(234)

In [39]: random.randint(0, 99)
Out[39]: 85

In [40]: random.randint(0, 99)
Out[40]: 50

In [41]: random.seed(234)

In [42]: random.randint(0, 99)
Out[42]: 86

In [43]: random.randint(0, 99)
Out[43]: 92
+4
2

, , - IPython random , Mersenne Twister. , random, , IPython .

, ( Python 2, Python 3), <Enter> random.randint ( random.random ). Python 3.6.2 IPython 6.2.0 macOS 10.12.6.

In [1]: import random

In [2]: random.seed(234)

In [3]: 

In [3]: 

In [3]: random.random()
Out[3]: 0.8579160018299248

In [4]: random.random()
Out[4]: 0.5055065431394443

In [5]: random.seed(234)

In [6]: random.random()
Out[6]: 0.26476014305349627

In [7]: random.random()
Out[7]: 0.8579160018299248

In [8]: random.random()
Out[8]: 0.5055065431394443

, random.random random.py , random:

def random(self):
    print("random being called")
    import traceback; traceback.print_stack()
    return super(Random, self).random()

IPython, hey presto! . ( ), :

  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/IPython/terminal/interactiveshell.py", line 376, in prompt_for_code
    pre_run=self.pre_prompt, reset_current_buffer=True)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/prompt_toolkit/interface.py", line 415, in run
    self.eventloop.run(self.input, self.create_eventloop_callbacks())
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/prompt_toolkit/eventloop/posix.py", line 157, in run
    random.shuffle(tasks)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/random.py", line 278, in shuffle
    j = randbelow(i+1)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/random.py", line 250, in _randbelow
    r = random()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/random.py", line 98, in random
    import traceback; traceback.print_stack()

, prompt_toolkit, IPython, ( , CHANGELOG).

, random.random :

In [1]: from random import Random

In [2]: my_random = Random()

In [3]: my_random.seed(234)

In [4]: my_random.randint(0, 99)
Out[4]: 43

In [5]: my_random.randint(0, 99)
Out[5]: 33

In [6]: my_random.seed(234)

In [7]: my_random.randint(0, 99)
Out[7]: 43

In [8]: my_random.randint(0, 99)
Out[8]: 33
+7

My Python 2.7.5 ,  (https://docs.python.org/2/library/random.html)

a None int long, hash (a). , - , PYTHONHASHSEED .

( ) , -. PYTHONHASHSEED?

-1

Source: https://habr.com/ru/post/1686879/

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