with addlockcount count time sleep( with addlockcount count auto acquire/release around stmt only thread updating at once addlock threading lock(threads [for in range( )thread threading thread(target=adderargs=(addlock,)thread start(threads append(threadfor thread in threadsthread join(print(countalthough some basic operations in the python language are atomic and need not be synchronizedyou're probably better off doing so for every potential concurrent update not only might the set of atomic operations change over timebut the internal implementation of threads in general can as well (and in factit may in python as described aheadof coursethis is an artificial example (spawning threads to add twice isn' exactly real-world use case for threads!)but it illustrates the issues that threads must address for any sort of potentially concurrent updates to shared object or name luckilyfor many or most realistic applicationsthe queue module of the next section can make thread synchronization an automatic artifact of program structure before we move aheadi should point out that besides thread and lockthe threading module also includes higher-level objects for synchronizing access to shared items ( semaphoreconditionevent)--many morein factthan we have space to cover heresee the library manual for details for more examples of threads and forks in generalsee the remainder this as well as the examples in the gui and network scripting parts of this book we will thread guisfor instanceto avoid blocking themand we will thread and fork network servers to avoid denying service to clients we'll also explore the threading module' approach to program exits in the absence of join calls in conjunction with queues--our next topic the queue module you can synchronize your threadsaccess to shared resources with locksbut you often don' have to as mentionedrealistically scaled threaded programs are often structured as set of producer and consumer threadswhich communicate by placing data onand taking it off ofa shared queue as long as the queue synchronizes access to itselfthis automatically synchronizes the threadsinteractions parallel system tools