如何将从子进程传递到父进程的列表添加到python中已有的列表

Question

我将一个列表从 a 传递subprocess到父进程，并且在父进程中我想将其添加到已经存在的列表中。我这样做了：

子进程脚本.py：

def func():

    list = []
    list.append('1')
    list.append('2')

    print'Testing the list passing'
    print '>>> list:',list

if __name__ == '__main__':
     func()

父脚本.py：

list1 = []
list1.append('a')
list1.append('b')
ret = subprocess.Popen([sys.executable,"/Users/user1/home/subprocess_script.py"],stdout=subprocess.PIPE)
ret.wait()

return_code = ret.returncode
out, err = ret.communicate()
if out is not None:
        for line in out.splitlines():

            if not line.startswith('>>>'):
                continue
            value = line.split(':',1)[1].lstrip()
            list1.extend(value)
print 'Final List: ',list1

但是当我执行此操作时，我没有得到所需的输出。我想要的最终列表应该是：['a','b','1','2']。但我明白['a', 'b', '[', "'", '1', "'", ',', ' ', "'", '2', "'", ']']哪个是错误的。我在这里做错了什么？

Answer 1

You are doing it wrongly.

When you do - print '>>> list:',list . It would print -

>>> list: [1, 2]

And when you do - value = line.split(':',1)[1].lstrip() , value would become the string -

'[1, 2]'

And when extending list1 with value , each character in value would be added as a new element in list1 (because it would iterate over each element of the string, which is each character and add them to the list1).

When creating the value , you want to remove the first [ as well as the trailed ] and then split them based on , .

Example code -

value = line.split(':',1)[1].lstrip().lstrip('[').rstrip(']').replace("'",'').replace(" ",'').split(',')

The above code is a very big hack , better would be to use ast.literal_eval as @logc mentioned in his answer -

import ast
value = ast.literal_eval(line.split(":",1)[1].lstrip())

But please be vary, that ast.literal_eval would evalutate the expression and return the result, you should use it with care.