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これは日々の作業を通して学んだことや毎日の生活で気づいたことをを記録しておく備忘録である。
HTML ファイル生成日時: 2026/03/09 21:11:11.534 (台灣標準時)
以下の Python のコードを Python 3.14 で実行しようとしたら、うまくいか なかったでござる。
#!/usr/pkg/bin/python3.13 # # Time-stamp: <2025/09/08 12:58:37 (UT+08:00) daisuke> # # importing multiprocessing module import multiprocessing # number of CPUs to be used n_cpu = 4 # output file name file_output = 'prime_numbers_4.data' # start and end numbers n_start = 2 n_end = 10**5 # function to check whether or not the number is a prime number def is_prime_number (x): # resetting parameter "pn" pn = 1 # examining if the number is divisible by numbers between 2 and (x-1) for k in range (2, x): # if the number is divisible by k if (x % k == 0): # then subtract 1 from "pn" pn -= 1 # leaving from the loop break # returning number and a flag "pn" return (x, pn) # numbers to be checked numbers = range (n_start, n_end + 1) # making a pool of workers pool = multiprocessing.Pool (n_cpu) # executing function for different numbers in parallel results = pool.map (is_prime_number, numbers) # opening file for writing with open (file_output, 'w') as fh_out: # for each number in the list "list_pn" for x, pn in results: # writing number to the file if (pn): fh_out.write (f'{x}\n')
以下のようなメッセージが表示されたでござる。
% python3.14 appy_s02_07_01.py Traceback (most recent call last): File "", line 1, in from multiprocessing.forkserver import main; main(16, 17, ['__main__'], **{'sys_path': ['/tmp', '/usr/pkg/lib/python314.zip', '/usr/pkg/lib/python3.14', '/usr/pkg/lib/python3.14/lib-dynload', '/usr/pkg/lib/python3.14/site-packages'], 'main_path': '/tmp/appy_s02_07_01.py', 'authkey_r': 19}) ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/forkserver.py", line 217, in main spawn.import_main_path(main_path) ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/spawn.py", line 307, in import_main_path _fixup_main_from_path(main_path) ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/spawn.py", line 297, in _fixup_main_from_path main_content = runpy.run_path(main_path, run_name="__mp_main__") File " ", line 287, in run_path File " ", line 98, in _run_module_code File " ", line 88, in _run_code File "/tmp/appy_s02_07_01.py", line 39, in pool = multiprocessing.Pool (n_cpu) File "/usr/pkg/lib/python3.14/multiprocessing/context.py", line 119, in Pool return Pool(processes, initializer, initargs, maxtasksperchild, context=self.get_context()) File "/usr/pkg/lib/python3.14/multiprocessing/pool.py", line 215, in __init__ self._repopulate_pool() ~~~~~~~~~~~~~~~~~~~~~^^ File "/usr/pkg/lib/python3.14/multiprocessing/pool.py", line 306, in _repopulate_pool return self._repopulate_pool_static(self._ctx, self.Process, ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^ self._processes, ^^^^^^^^^^^^^^^^ ...<3 lines>... self._maxtasksperchild, ^^^^^^^^^^^^^^^^^^^^^^^ self._wrap_exception) ^^^^^^^^^^^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/pool.py", line 329, in _repopulate_pool_static w.start() ~~~~~~~^^ File "/usr/pkg/lib/python3.14/multiprocessing/process.py", line 121, in start self._popen = self._Popen(self) ~~~~~~~~~~~^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/context.py", line 300, in _Popen return Popen(process_obj) File "/usr/pkg/lib/python3.14/multiprocessing/popen_forkserver.py", line 35, in __init__ super().__init__(process_obj) ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/popen_fork.py", line 20, in __init__ self._launch(process_obj) ~~~~~~~~~~~~^^^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/popen_forkserver.py", line 42, in _launch prep_data = spawn.get_preparation_data(process_obj._name) File "/usr/pkg/lib/python3.14/multiprocessing/spawn.py", line 164, in get_preparation_data _check_not_importing_main() ~~~~~~~~~~~~~~~~~~~~~~~~~^^ File "/usr/pkg/lib/python3.14/multiprocessing/spawn.py", line 140, in _check_not_importing_main raise RuntimeError(''' ...<16 lines>... ''') 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. To fix this issue, refer to the "Safe importing of main module" section in https://docs.python.org/3/library/multiprocessing.html Traceback (most recent call last): File "/tmp/appy_s02_07_01.py", line 39, in pool = multiprocessing.Pool (n_cpu) File "/usr/pkg/lib/python3.14/multiprocessing/context.py", line 119, in Pool return Pool(processes, initializer, initargs, maxtasksperchild, context=self.get_context()) File "/usr/pkg/lib/python3.14/multiprocessing/pool.py", line 215, in __init__ self._repopulate_pool() ~~~~~~~~~~~~~~~~~~~~~^^ File "/usr/pkg/lib/python3.14/multiprocessing/pool.py", line 306, in _repopulate_pool return self._repopulate_pool_static(self._ctx, self.Process, ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^ self._processes, ^^^^^^^^^^^^^^^^ ...<3 lines>... self._maxtasksperchild, ^^^^^^^^^^^^^^^^^^^^^^^ self._wrap_exception) ^^^^^^^^^^^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/pool.py", line 329, in _repopulate_pool_static w.start() ~~~~~~~^^ File "/usr/pkg/lib/python3.14/multiprocessing/process.py", line 121, in start self._popen = self._Popen(self) ~~~~~~~~~~~^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/context.py", line 300, in _Popen return Popen(process_obj) File "/usr/pkg/lib/python3.14/multiprocessing/popen_forkserver.py", line 35, in __init__ super().__init__(process_obj) ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/popen_fork.py", line 20, in __init__ self._launch(process_obj) ~~~~~~~~~~~~^^^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/popen_forkserver.py", line 51, in _launch self.sentinel, w = forkserver.connect_to_new_process(self._fds) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/forkserver.py", line 106, in connect_to_new_process connection.answer_challenge( ~~~~~~~~~~~~~~~~~~~~~~~~~~~^ wrapped_client, self._forkserver_authkey) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/pkg/lib/python3.14/multiprocessing/connection.py", line 970, in answer_challenge message = connection.recv_bytes(256) # reject large message File "/usr/pkg/lib/python3.14/multiprocessing/connection.py", line 222, in recv_bytes buf = self._recv_bytes(maxlength) File "/usr/pkg/lib/python3.14/multiprocessing/connection.py", line 447, in _recv_bytes buf = self._recv(4) File "/usr/pkg/lib/python3.14/multiprocessing/connection.py", line 416, in _recv raise EOFError EOFError
https://docs.python.org/3/library/multiprocessing.html の "Safe importing of main module" の部分を見るように、との ことなので、その部分を見てみたでござる。 multiprocessing を使って実行 する関数を、 if __name__ == '__main__': の中に入れないとい けないようでござる。
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コードを以下のように変更したら、エラーが出なくなったでござる。
#!/usr/bin/env python3 # # Time-stamp: <2026/03/03 11:32:11 (UT+08:00) daisuke> # # importing multiprocessing module import multiprocessing # number of CPUs to be used n_cpu = 4 # output file name file_output = 'prime_numbers_4.data' # start and end numbers n_start = 2 n_end = 10**5 # function to check whether or not the number is a prime number def is_prime_number (x): # resetting parameter "pn" pn = 1 # examining if the number is divisible by numbers between 2 and (x-1) for k in range (2, x): # if the number is divisible by k if (x % k == 0): # then subtract 1 from "pn" pn -= 1 # leaving from the loop break # returning number and a flag "pn" return (x, pn) # numbers to be checked numbers = range (n_start, n_end + 1) # executing the function if __name__ == '__main__': # making a pool of workers pool = multiprocessing.Pool (n_cpu) # executing function for different numbers in parallel results = pool.map (is_prime_number, numbers) # opening file for writing with open (file_output, 'w') as fh_out: # for each number in the list "list_pn" for x, pn in results: # writing number to the file if (pn): fh_out.write (f'{x}\n')