无法从另一个python .py文件运行进程
问题描述:
我正在创建一个类,并且在初始化它时,我正在调用(多进程)它的函数。当我从相同的.py文件创建此类时,一切正常。但是,当我从另一个.py文件初始化此类时 - 它会失败并引发错误...为什么?无法从另一个python .py文件运行进程
MyDummyClass.py:
import multiprocessing
class MyDummyClass:
def __init__(self):
print("I am in '__init__()'")
if __name__ == 'MyDummyClass':
p = multiprocessing.Process(target=self.foo())
p.start()
def foo(self):
print("Hello from foo()")
example.py:
from MyDummyClass import MyDummyClass
dummy = MyDummyClass()
当我运行example.py,我收到此错误:
I am in '__init__()'
Hello from foo()
I am in '__init__()'
Hello from foo()
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "C:\Python\lib\multiprocessing\spawn.py", line 105, in spawn_main
exitcode = _main(fd)
File "C:\Python\lib\multiprocessing\spawn.py", line 114, in _main
prepare(preparation_data)
File "C:\Python\lib\multiprocessing\spawn.py", line 225, in prepare
_fixup_main_from_path(data['init_main_from_path'])
File "C:\Python\lib\multiprocessing\spawn.py", line 277, in _fixup_main_from_path
run_name="__mp_main__")
File "C:\Python\lib\runpy.py", line 263, in run_path
pkg_name=pkg_name, script_name=fname)
File "C:\Python\lib\runpy.py", line 96, in _run_module_code
mod_name, mod_spec, pkg_name, script_name)
File "C:\Python\lib\runpy.py", line 85, in _run_code
exec(code, run_globals)
File "E:\Dropbox\Docs\Business\_NZTrackAlerts\Website\Current dev\NZtracker\cgi-bin\example1.py", line 2, in <module>
dummy = MyDummyClass()
File "...path to my file...\MyDummyClass.py", line 13, in __init__
p.start()
File "C:\Python\lib\multiprocessing\process.py", line 105, in start
self._popen = self._Popen(self)
File "C:\Python\lib\multiprocessing\context.py", line 223, in _Popen
return _default_context.get_context().Process._Popen(process_obj)
File "C:\Python\lib\multiprocessing\context.py", line 322, in _Popen
return Popen(process_obj)
File "C:\Python\lib\multiprocessing\popen_spawn_win32.py", line 33, in __init__
prep_data = spawn.get_preparation_data(process_obj._name)
File "C:\Python\lib\multiprocessing\spawn.py", line 143, in get_preparation_data
_check_not_importing_main()
File "C:\Python\lib\multiprocessing\spawn.py", line 136, in _check_not_importing_main
is not going to be frozen to produce an executable.''')
RuntimeError:
An attempt has been made to start a new process before the
current process has finished its bootstrapping phase.
This probably means that you are not using fork to start your
child processes and you have forgotten to use the proper idiom
in the main module:
if __name__ == '__main__':
freeze_support()
...
The "freeze_support()" line can be omitted if the program
is not going to be frozen to produce an executable.
我不明白(而不是来回m其他职位)如何解决它。
非常感谢您的帮助!
答
这与python实际执行脚本的方式有关。抛出的错误基本上说,当python还没有准备好时,你正试图开始一个新的进程。这是因为你在主脚本中调用了dummy = MyDummyClass()
而没有给python一个完全初始化的机会。如果你不是有example.py
这样的:
from MyDummyClass import MyDummyClass
if __name__ == "__main__":
dummy = MyDummyClass()
这将产生所需输出:
C:\Python Scripts>python example.py
I am in '__init__()'
Hello from foo()
的if __name__ == "__main__"
块告诉蟒蛇“只有当脚本正在运行为主脚本执行这个(即python example.py
),这将强制python在运行该块之前正确初始化所有内容。
道歉,如果此答案没有足够的描述python后端发生了什么,因为它正在做初始化,我自己也不知道一吨:)
非常感谢@乙醚(+1)!它确实有效。也就是说,我的真实程序要复杂得多(我已经在这里放了一个简单的例子)。也就是说,如果我在main(或“example.py”,如这里)中添加[if __name__ ==“__main__”],会发生什么?程序是否等待一切都被初始化,然后才调用其他类的初始化?它是否等待?或会发生什么?非常感谢你! – Yura
所以这里有一个实验:尝试在你的MyDummyClass声明文件中添加相同的'if name = main'块并运行'example.py'。你会看到那个代码没有运行,因为你没有将该脚本作为主脚本运行!当python导入脚本时,它会在导入时执行脚本全局范围内的所有代码。将'name main'块放在一个脚本中告诉python如果它正在导入它,就不要执行它,并且只在它是主要的时候(以及初始化之后)执行。此外,如果我的答案奏效,你介意将它标记为接受的答案:) – AetherUnbound
谢谢@AetherUnboud。当然(标记为答案)。是的,我试了一下,并没有奏效(如预期)。我所问的是关于**初始化会发生什么**?主进程是否会“等待”,直到所有内容都被安全地初始化,然后运行其他类和它们的多进程? – Yura