通過字符串在外部模塊中調用Python函數

Question

我有一個遺傳算法將使用的手動維護的python函數和模塊列表，我希望能夠重復調用它們並監視結果。

test_exec.py

import os
from random import randint

def main():
    toolList = [{'file':'test1.py', 'function':'sum_even_numbers', 'args':['list'], 'return':['int']},
                {'file':'test1.py', 'function':'get_min_even_num', 'args':['list'], 'return':['int']}   ]
    for tool in toolList:
        for i in range(0,3):
            run(tool, [randint(10,99) for j in range(1,randint(2,5))])

def run(tool, args):
    mod = __import__( os.path.basename(tool['file']).split('.')[0])
    func = getattr(mod, tool['function'])
    tool['return'] = func(args)
    print('main called ' + tool['file'] + '->' + tool['function'] + ' with ', args, ' = ', tool['return'])

main()

test1.py

def sum_even_numbers(numbers):
    return sum([i for i in numbers if i % 2 == 0])

def get_min_even_num(numbers):
    return min([i for i in numbers if i % 2 == 0])

# other code in test1.py which we dont want to execute
print('test1.py has been run' )

代碼的結果：

test1.py has been run
('main called test1.py->sum_even_numbers with ', [30, 66, 25, 45], ' = ', 96)
('main called test1.py->sum_even_numbers with ', [92], ' = ', 92)
('main called test1.py->sum_even_numbers with ', [59, 73], ' = ', 0)
('main called test1.py->get_min_even_num with ', [59, 12, 61, 24], ' = ', 12)
('main called test1.py->get_min_even_num with ', [22], ' = ', 22)
('main called test1.py->get_min_even_num with ', [97, 94], ' = ', 94)

該代碼通過按字符串調用模塊中的函數而起作用，但是在導入過程中，它將執行整個文件。 有沒有更好的方法可以做到這一點，以使整個模塊都不會運行？

Answer 1

當您從模塊（甚至是獨立的模塊級函數）中導入某些內容時，python解釋器必須先解析/編譯整個文件，然后才能訪問該函數。

在def的情況下，這是無害的-它們只是編譯成函數，不會造成傷害。 但是有時您會遇到“您不想運行的代碼”，例如示例中的print 。

導入模塊時，阻止代碼執行的規范方法是：

if __name__ == '__main__':
    # code that only gets executed when I explicitly run this module

更多閱讀。