I'd like to launch *and control* a long thread. I want to print the
progress of the long thread in the main thread. It's a GUI script, here
it's a console script only to simplify.
import threading
import time
class MyClass:
def start(self):
self.max = 5
self.pause = 1
t = threading.Thread(target=self.thread)
t.start()
i = -1
while self.cnt != self.max - 1:
if i != self.cnt:
print("{:d}".format(self.cnt))
i = self.cnt
print("Finished")
def thread(self):
for i in range(self.max):
self.cnt = i
time.sleep(self.pause)
c = MyClass()
c.start()
It seems it works, but I'm not sure it is the correct way to share the
variable self.cnt. It is only written in the long thread and only read
in the main thread.
Could a single Python instruction be interrupted (in this case, self.cnt
= i)? Should I use a locking mechanism when reading/writing?
What about if the variable is more complex, for example a list or
dictionary? Even in this case, is it safe to avoid locking on a shared
variable if the operation on the variable is performed in a single
Python instruction?
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