python Manager 之dict KeyError问题详解程序员

程序需要多进程见共享内存，使用了Manager的dict。最初代码如下：

from multiprocessing import Process, Manager 
d = Manager().dict() 
d2 = {} 
 
def f(): 
    d['a1'] = {} 
 <span style="color:#ff6666;">   d['a1']['a2'] = 11 
    print d['a1']['a2'] 
 
if __name__ == '__main__': 
    p = Process(target=f) 
    p.start() 
    p.join() 

结果报错：

    print d['a1']['a2'] 
KeyError: 'a2'

解决方案：

from multiprocessing import Process, Manager 
d = Manager().dict() 
d2 = {} 
 
def f(): 
    d['a1'] = {} 
<span style="color:#ff6666;">    d2['a2'] = 11 
    d['a1'] = d2 
    print d['a1']['a2'] 
 
if __name__ == '__main__': 
    p = Process(target=f) 
    p.start() 
    p.join()