为什么在外部执行 Python 文件时会出现“NameError: name not defined”？

Question

我有运行函数以从 API 检索项目的多处理代码：

import os
import pandas as pd
from multiprocessing import Pool
from datetime import timedelta, date
from external_functions import get_api_item #separate .py file with a function

def date_range(start_date, end_date):
    for n in range(int ((end_date - start_date).days)):
        yield start_date + timedelta(n)

start_date = date(2020, 1, 29)
end_date = date(2020, 1, 30)
date_list = []

for single_date in date_range(start_date, end_date):
    date_list.append(single_date.strftime('%Y-%m-%d'))

if __name__ == '__main__':
    global results
    p = Pool(20)
    results = p.map(get_api_item, date_list)
    p.terminate()
    p.join()

result = pd.concat(results)

当我从 Jupyter Notebook、Spyder 等运行此代码时，它可以工作。当我从 SSIS 中的 Execute Process 任务执行它时，我收到此错误：

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "E:\Python\Anaconda3\lib\multiprocessing\spawn.py", line 105, in spawn_ma
in
    exitcode = _main(fd)
  File "E:\Python\Anaconda3\lib\multiprocessing\spawn.py", line 114, in _main
    prepare(preparation_data)
  File "E:\Python\Anaconda3\lib\multiprocessing\spawn.py", line 225, in prepare
    _fixup_main_from_path(data['init_main_from_path'])
  File "E:\Python\Anaconda3\lib\multiprocessing\spawn.py", line 277, in _fixup_m
ain_from_path
    run_name="__mp_main__")
  File "E:\Python\Anaconda3\lib\runpy.py", line 263, in run_path
    pkg_name=pkg_name, script_name=fname)
  File "E:\Python\Anaconda3\lib\runpy.py", line 96, in _run_module_code
    mod_name, mod_spec, pkg_name, script_name)
  File "E:\Python\Anaconda3\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "<path to api>\api.py", line 29, in <module>
    result = pd.concat(results)
NameError: name 'results' is not defined

这告诉我函数本身实际上并没有运行/完成将results 提供给下一行。为什么会这样？

如果我删除 if __name__ == '__main__': 并直接运行它，我会收到此错误：

  File "E:\Python\Anaconda3\lib\multiprocessing\spawn.py", line 143, in get_prep
aration_data
    _check_not_importing_main()
  File "E:\Python\Anaconda3\lib\multiprocessing\spawn.py", line 136, in _check_n
ot_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.

Answer 1

if __name__ == '__main__' 行专门检查文件的调用位置，如果您直接调用它，则名称等于 main，但是如果您从服务中运行它，则名称基于调用的任何服务它。您会收到名称错误，因为 results 仅在该 if 语句中定义。 （由于您使用全局，这不是范围问题）

我一直在用谷歌搜索看看 SSIS 实例的名称是什么，但没有找到任何东西。

更多关于__name__=='__main__'：

What does if __name__ == "__main__": do?