I'm creating a multiprocess, which creates a csv file. When I run the code with d.daemon = False
it works fine, ie it creates a file in the same folder. But when compiled and run with d.daemon = True
, it does not, ie does not creates a file. Why's so?
I've a seed list of URLs from which I need to scrape the data.
for url in config.SEED_LIST:
# starting a new process for each category.
d = multiprocessing.Process(target=workers.scrape, args=())
d.daemon = True
d.start()
def scrape():
import time
time.sleep(5)
# The above part of code takes some time to scrape a webpage, applying
# some logic, which takes some time to execute, hence I've added a time
# sleep of 5 secs. But when run with daemon = True, the file is not
# created. Else it works fine.
data = [[1, 2, 3, 4], [2224, 34, 34, 34, 34]]
with open('1.csv', "wb") as f:
writer = csv.writer(f)
writer.writerows(data)
According to multiprocess daemon documentation by setting d.daemon=True
when your script ends its job will kill all subprocess. That occurs before they can start to write so no output will be produced.
d.daemon = True
means that the subprocess is automatically terminated after the parent process ends to prevent orphan processes. join()
is helpful by simply adding d.join()
after d.start()
, so that the parent process does not end before the child process; instead, the parent process will wait until the child process ends.
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