In Python for *nix, does time.sleep() block the thread or the process?

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7 Answers

It blocks the thread. If you look in Modules/timemodule.c in the Python source, you'll see that in the call to floatsleep(), the substantive part of the sleep operation is wrapped in a Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS block, allowing other threads to continue to execute while the current one sleeps. You can also test this with a simple python program:

import time from threading import Thread class worker(Thread): def run(self): for x in xrange(0,11): print x time.sleep(1) class waiter(Thread): def run(self): for x in xrange(100,103): print x time.sleep(5) def run(): worker().start() waiter().start()

Which will print:

>>> thread_test.run() 0 100 >>> 1 2 3 4 5 101 6 7 8 9 10 102
6

It will just sleep the thread except in the case where your application has only a single thread, in which case it will sleep the thread and effectively the process as well.

The python documentation on sleep() doesn't specify this however, so I can certainly understand the confusion!

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Just the thread.

The thread will block, but the process is still alive.

In a single threaded application, this means everything is blocked while you sleep. In a multithreaded application, only the thread you explicitly 'sleep' will block and the other threads still run within the process.

Only the thread unless your process has a single thread.

Process is not runnable by itself. In regard to execution, process is just a container for threads. Meaning you can't pause the process at all. It is simply not applicable to process.

3

it blocks a thread if it is executed in the same thread not if it is executed from the main code