为什么这个 forloop 会跳过列表中的项目？

Question

当我运行下面的代码时，它似乎只遍历了列表中所有工人列表的一半。然后它跳转到关闭父进程。

我非常困惑，为什么下面的代码没有遍历列表中的所有项目，也许我盯着这个看得太久了，看不出明显的东西？任何帮助将不胜感激。

这是控制台输出。

Waiting...
[u'worker-1.15579', u'worker-1.15575', u'worker-1.15577', u'worker-1.15570', u'worker-1.15573', u'worker-1.15168', u'worker-1.15170']
The terminate_pid is 15561
Process was SUCCESSFULLY closed.
Process was SUCCESSFULLY closed.
Process was SUCCESSFULLY closed.
no process found with pid 15170
Process was already closed.
Closed terminator window.

下面是代码，

            workers_to_be_restarted = [u'worker-1.14524', u'worker-1.14526', u'worker-1.14518', u'worker-1.14528', u'worker-1.14522']

            for item in workers_to_be_restarted:
                if this_machine == item.split('.')[0]:
                    if not terminate_pid:
                        try:
                            terminate_pid = psutil.Process(psutil.Process( int(item.split('.')[1]) ).ppid()).ppid()
                            print "The terminate_pid is {}".format(str(terminate_pid))
                        except Exception, e:
                            terminate_pid = None
                            print e
                            pass
                    try:
                        print "Terminating {}".format(item)
                        p = psutil.Process( int(item.split('.')[1]) )
                        p.terminate()
                        time.sleep(1)
                        print "Process was SUCCESSFULLY closed."
                        workers_to_be_restarted.remove( item )
                    except Exception, e:
                        print e
                        time.sleep(1)
                        print "Process was already closed."
                        workers_to_be_restarted.remove( item )
                        pass
            try: #THE ABOVE SEEMS TO BE EXITING HERE before looping through all the items!? NOT SURE WHY?
                if terminate_pid:
                    p = psutil.Process( terminate_pid )
                    p.terminate()
                    print "Closed terminator window."
                    worker_restart['restart'] = None
                    worker_restart['workers_to_be_restarted'] = workers_to_be_restarted

Answer 1

当您修改正在迭代的列表时会发生这种情况：

foo = [1, 2, 3, 4, 5]

for each in foo:
    if each == 2:
        foo.remove(each)

    print each


>>> 1
>>> 2
>>> 4
>>> 5

要解决这个问题，您可以将列表复制到一个新列表中，然后从副本（而不是您正在迭代的那个）中删除：

foo = [1, 2, 3, 4, 5]
bar = list(foo)

for each in foo:
    if each == 2:
        bar.remove(each)

    print each

print bar

>>> 1
>>> 2
>>> 3
>>> 4
>>> 5
>>> [1, 3, 4, 5]

Answer 2

看起来您只是在迭代一部分的原因是 workers_to_be_restarted.remove( item )。这实际上是删除列表中的 next 项目，而不是您打算删除的项目。例如：

workers_to_be_restarted = [u'worker-1.14524', u'worker-1.14526', u'worker-1.14518', u'worker-1.14528', u'worker-1.14522']
for item in workers_to_be_restarted:
    print(item)
    workers_to_be_restarted.remove(item)

输出：

worker-1.14524
worker-1.14518
worker-1.14522

如您所见，第二个和第四个工人在迭代其他工人时被删除。要解决此问题，请先 copy 列表并对其进行迭代。我会用这样的完整列表切片分配替换您当前的行：

for item in workers_to_be_restarted[:]:

输出：

worker-1.14524
worker-1.14526
worker-1.14518
worker-1.14528
worker-1.14522

为什么这个 forloop 会跳过列表中的项目？

Why is this forloop skipping items in the list?

python

for-loop

try-catch