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I am pretty new to python. I am trying to dynamically create some threads but am getting some errors. Can you help me please. If you don't like my code feel free to give me advices.

This is the code:

from multiprocessing import Process
...    
for x in range(1, 6):
    globals()['p%s' % x] = Process(target=findContent, args=(fileList[curr:curr + fileAmount],))
    curr += fileAmount
    globals()['p%s' % x].start()
    globals()['p%s' % x].join()

And this is the error:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\multiprocessing\spawn.py", line 105, in spawn_main
    exitcode = _main(fd)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\multiprocessing\spawn.py", line 114, in _main
    prepare(preparation_data)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\multiprocessing\spawn.py", line 225, in prepare
    _fixup_main_from_path(data['init_main_from_path'])
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\multiprocessing\spawn.py", line 277, in _fixup_main_from_path
    run_name="__mp_main__")
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\runpy.py", line 263, in run_path
    pkg_name=pkg_name, script_name=fname)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\runpy.py", line 96, in _run_module_code
    mod_name, mod_spec, pkg_name, script_name)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "E:\test\.scanCombolistsMultiThreading.py", line 207, in <module>
    splitFileList()
  File "E:\test\.scanCombolistsMultiThreading.py", line 92, in splitFileList
    globals()['p%s' % x].start()
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\multiprocessing\process.py", line 112, in start
    self._popen = self._Popen(self)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\multiprocessing\context.py", line 223, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\multiprocessing\context.py", line 322, in _Popen
    return Popen(process_obj)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\multiprocessing\popen_spawn_win32.py", line 33, in __init__
    prep_data = spawn.get_preparation_data(process_obj._name)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\lib\multiprocessing\spawn.py", line 143, in get_preparation_data
    _check_not_importing_main()
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python37-32\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.
NineThree
  • 76
  • 6
  • I assume a missing `if __name__ == '__main__'` around the start of the processes causes this (see also [this Q&A](https://stackoverflow.com/questions/18204782/runtimeerror-on-windows-trying-python-multiprocessing/18205006)). Your code will not run in parallel, because you wait for each process to complete before starting the next one (i.e. the `.join()` call should be _outside_ the for loop). Not sure if altering the symbol table by creating/altering items on the return value of `globals()` can be considered a good practice :) – shmee Nov 26 '18 at 12:04
  • Possible duplicate of [RuntimeError on windows trying python multiprocessing](https://stackoverflow.com/questions/18204782/runtimeerror-on-windows-trying-python-multiprocessing) – shmee Nov 26 '18 at 12:05

0 Answers0