cross python version randomness

Robin Becker robin at reportlab.com
Mon Mar 20 12:32:05 EDT 2017


Is there a way to get the same sequences of random numbers in python 2.7 and 
python >= 3.3?

I notice that this simple script produces different values in python 2.7 and >=3.3

C:\code\hg-repos\reportlab>cat s.py
import sys, random
print(sys.version)
random.seed(103)
for i in range(5):
     print(i, random.randint(10,25))

C:\code\hg-repos\reportlab>\python27\python s.py
2.7.13 (v2.7.13:a06454b1afa1, Dec 17 2016, 20:53:40) [MSC v.1500 64 bit (AMD64)]
0 25
1 17
2 21
3 21
4 13

C:\code\hg-repos\reportlab>\python33\python s.py
3.3.5 (v3.3.5:62cf4e77f785, Mar  9 2014, 10:35:05) [MSC v.1600 64 bit (AMD64)]
0 24
1 16
2 12
3 13
4 22

However, when I use random.random() all seems to be the same so this script
C:\code\hg-repos\reportlab>cat u.py
import sys, random
print(sys.version)
random.seed(103)
for i in range(5):
     print(i, random.random())

seems to be fine


C:\code\hg-repos\reportlab>\python27\python u.py
2.7.13 (v2.7.13:a06454b1afa1, Dec 17 2016, 20:53:40) [MSC v.1500 64 bit (AMD64)]
(0, 0.9790501200727744)
(1, 0.45629827629184827)
(2, 0.7188470341002364)
(3, 0.7348862425853395)
(4, 0.21490166849706338)

C:\code\hg-repos\reportlab>\python33\python u.py
3.3.5 (v3.3.5:62cf4e77f785, Mar  9 2014, 10:35:05) [MSC v.1600 64 bit (AMD64)]
0 0.9790501200727744
1 0.45629827629184827
2 0.7188470341002364
3 0.7348862425853395
4 0.21490166849706338

presumably randint is doing something different to get its values.
-- 
Robin Becker



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