if __name__ == '__mp_main__':
    import sys
    sys.path = ['', '/home/arigo/pypysrc', '/home/arigo/lib/python', '/opt/pypy3/lib_pypy/__extensions__', '/opt/pypy3/lib_pypy', '/opt/pypy3/lib-python/3', '/opt/pypy3/lib-python/3/lib-tk', '/opt/pypy3/lib-python/3/plat-linux2', '/home/arigo/.local/lib/python3.5/site-packages', '/opt/pypy3/site-packages']

import multiprocessing as mp
import time
 
def foo(x):
    return x**2
 
if __name__ == '__main__':
    mp.set_start_method('spawn')
    mp.set_executable('/usr/bin/pypy3')
   
    pool = mp.Pool(1)
    pool.apply_async(foo, args=(12,), callback=print)
    time.sleep(1)