Multiprocessing error: function not defined

Question

以下returns"NameError: name 'times_2' is not defined"，我也想不通为什么：

def pass_data(data): return times_2(data)

def times_2(data): return data*2

import multiprocessing
multiprocessing.pool = Pool()
pool.ncpus = 2
res = pool.map(pass_data, range(5))
print(res)

我实际上想做的是将函数应用于 pandas 数据框。但是，因为我不能使用 lambda 函数来执行此操作：

pool.map(lambda x: x.apply(get_weather, axis=1), df_split)

相反，我通过以下辅助方法获得了它，但它抛出了 "NameError: name 'get_weather' is not defined":

def get_weather(df):
    *do stuff*
    return weather_df

def pass_dataframe(df):
    return df.apply(get_weather, axis=1)

results = pool.map(pass_dataframe, df_split)

Answer 1

尝试像这样使用池：

from multiprocessing import Pool

def pass_data(data): return times_2(data)

def times_2(data): return data*2

with Pool(processes=4) as pool:
    res = pool.map(pass_data, range(5))
    print(res)

在 Windows:

from multiprocessing import Pool

def pass_data(data): return times_2(data)

def times_2(data): return data*2

if __name__ == '__main__':
    with Pool(processes=4) as pool:
        res = pool.map(pass_data, range(5))
        print(res)

查看文档 https://docs.python.org/3/library/multiprocessing.html#multiprocessing-programming

Multiprocessing error: function not defined

Multiprocessing error: function not defined

python-3.x

python-multiprocessing