Python threads in embedded Python: how?

Question

While experimenting with the Python Python API (python.org) C, I wondered how to correctly create threads through Python threadingwhen Python itself is embedded in a C program. Functions PyEval_EvalCodeand kin seem to complete the threads that it "owns" as soon as the C function completes the evaluation of the Python code block. For example, starting the next Python from C ...

import threading, time

class MyThread(threading.Thread):
    def __init__(self, num):
        self.num = num
        threading.Thread.__init__(self)
    def run(self):
        print "magic num = %d" % self.num

for x in xrange(1000):
    MyThread(x).start()

... will stop completely as soon as the for loop completes, and control returns from function PyEval_EvalCode(or such) C. We can observe that this gives a truncated output.

I suggested this behavior after using the following tactics: we can dictate when the control returns and, therefore, to some extent the result, by sleeping after spawning the spinning of threads:

for x in xrange(100):
    MyThread(x).start()

# Don't leave just yet; let threads run for a bit
time.sleep(5) # Adjust to taste

I suspect a possible approach is to create a new system thread dedicated to implementing and running Python. After spawning Python threads, Python code will sleep on a semaphore or something else until it is asked to close it. Then the question will be, how can I stream the thread to shut it down neatly? Similarly, the "main" block can simply join () for all threads; threads will then need to be signaled from C.

The solutions are greatly appreciated.

Answer 1

pthread? Python , ,