Jython随机模块为cpython产生不同的结果

Question

I'm generating some test data using a known random seed. I want to use this data from cpython and from jython. I've found that the data is different if I use jython (2.5.2) vs cpython.

Boiling it down to a simple test, I can see that the PRNG is giving different results in the two implementations:

In Jython:

Jython 2.5.2 (Release_2_5_2:7206, Mar 2 2011, 23:12:06) 
[Java HotSpot(TM) Server VM (Sun Microsystems Inc.)] on java1.6.0_26
Type "help", "copyright", "credits" or "license" for more information.
>>> import random
>>> random.seed(1)
>>> random.random()
0.7308781974052877

In CPython:

Python 2.7.2+ (default, Oct  4 2011, 20:03:08) 
[GCC 4.6.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import random
>>> random.seed(1)
>>> random.random()
0.13436424411240122

The test data I'm generating is reproducible within each python implementation. Is there a way around this? Maybe I need to code my own PRNG?

Answer 1

There is a way around this. Both implementations include the pure-python "WichmannHill" PRNG. It's slower but it gives the same results in both Jython and CPython.

In my code I replaced

random.seed(1)
uuid += random.choice(hexdigits)

with

rand = random.WichmannHill(1)
uuid += rand.choice(hexdigits)

Answer 2

As said by delnan in a comment: It is not a surprise that different python interpreters generate different random sequences. The official documentation refers to the C implementation of an algorithm. Other Python implementations may choose other algorithms. In fact, the lowest common denominator might be the distribution of the produced random sequences.

If you depend on pseudo-random sequences which can be reproduced across all Python interpreters you have to write your own pseudo-random number generator. A linear feedback shift register may be a good start and relatively easy to understand.