[Python-Dev] PEP 550 v4 (original) (raw)

francismb francismb at email.de
Sat Aug 26 16:45:07 EDT 2017

Hi,

Multithreaded Code ------------------

In multithreaded code, context variables behave like thread locals:: var = newcontextvar() def sub(): assert var.lookup() is None # The execution context is empty # for each new thread. var.set('sub') def main(): var.set('main') thread = threading.Thread(target=sub) thread.start() thread.join() assert var.lookup() == 'main' it's by design that the execution context for new threads to be empty or should it be possible to set it to some initial value? Like e.g:

 var = new_context_var('init')

 def sub():
     assert var.lookup() == 'init'
     var.set('sub')

 def main():
     var.set('main')

     thread = threading.Thread(target=sub)
     thread.start()
     thread.join()

     assert var.lookup() == 'main'

Thanks, --francis

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