why is __init__ module in django project loaded twice

Question

I put

print 'Hello world!'

into __init__.py in my django project. When I run ./manage.py runserver now, I get

gruszczy@gruszczy-laptop:~/Programy/project$ ./manage.py runserver
Hello world!
Hello world!
Validating models...
0 errors found

Why is __init__.py run twice? It should be loaded only once.

Answer 1

It should be loaded only once... per process. I'm guessing that manage.py forks, and that two separate processes are launched. Could you print the result of os.getpid()?

Answer 2

After learning the --noreload option from the above answer, I found that both

% django-admin help runserver
% manage.py help runserver

map to the below code in django/core/management/commands/runserver.py

parser.add_argument(
    '--noreload', action='store_false', dest='use_reloader',
    help='Tells Django to NOT use the auto-reloader.',
)

Both django-admin.py and manage.py call

django.core.management.execute_from_command_line(sys.argv) 

I then started to trace the Django code to better understand why the two PIDs when --noreload is not given.

In below, we have

class BaseCommand defined in management/base.py and 
class Command(BaseCommand) defined in management/commands/runserver.py

    execute_from_command_line(sys.argv) ==>> utility.execute() ==>>
    self.fetch_command(subcommand).run_from_argv(self.argv) ==>>
    self.execute(*args, **cmd_options) in management/base.py ==>>
        super().execute(*args, **options) in commands/runserver.py ==>>
    output = self.handle(*args, **options) in base.py ==>>
        self.run(**options) in commands/runserver.py  ==>>
    if use_reloader:
        autoreload.run_with_reloader(self.inner_run, **options)
    else:
        self.inner_run(None, **options)  // --noreload


    ParentPID run_with_reloader() ==>> DJANGO_AUTORELOAD_ENV = None ==>> 
    restart_with_reloader() only runs the 1st time by PPID ==>>
    ==>> subprocess.call(DJANGO_AUTORELOAD_ENV = true) ==>> child process cPID
    cPID run_with_reloader() ==>> "Watching for file changes with StatReloader"
    ==>> start_django(StatReloader, Command.inner_run) ==>>
    django_main_thread = threading.Thread(target=inner_run) and
    StatReloader.run(django_main_thread)
    ==>> Performing system checks... Starting development server at
    http://127.0.0.1:8080/

    The StatReloader(BaseReloader) will check file changes once per second.
    If there is a a file write => notify_file_changed(timestamp delta) =>
    trigger_reload() and PPID will spawn a new cPID and the old cPID is gone 
    so that we don't have to restart the runserver whenever there is a code change.

With the --noreload option, PPID executes inner_run() directly and skips the cPID subprocess for auto-reloading. If you kill either PPID or cPID, the whole process dies.