Call python 3 from python 2 virtualenv

2.py

from simpledate import *

for date in '1/6/2013 BST', '1/6/2013 EST', 'Tue, 18 Jun 2013 12:19:0$
    print(best_guess_utc(date))

2call3.py

import execnet
gw = execnet.makegateway("popen//python=/usr/bin/python3")
channel = gw.remote_exec("""
    from simpledate import *
    while 1:
        x = channel.receive()
        if x is None:
            break
        channel.send(best_guess_utc(x).isoformat())
""")
for x in '1/6/2013 BST', '1/6/2013 EST', 'Tue, 18 Jun 2013 12:19:09 -0400':
    channel.send(x)
    print channel.receive()
channel.send(None)

makeenv.sh

sudo pip3 install simple-date

virtualenv env
source env/bin/activate
pip install execnet
python 2call3.py

result.txt

$ cat 2call3.py | pypy -m timeit -n 10000
10000 loops, best of 3: 0.0016 usec per loop
$ cat 2.py | pypy -m timeit -n 10000     
10000 loops, best of 3: 0.00241 usec per loop