Python中循环删除列表中元素的怪异行为

Question

我知道，如果当前正在迭代列表中的某个元素，则不能从该列表中移除该元素。然后我要做的是将不想删除的元素从那个列表复制到另一个列表中，然后用新列表替换原来的列表。以下是我的相关代码：

while len(tokenList) > 0:
    # loop through the tokenList list

    # reset the updated token list and the remove flag
    updatedTokenList = []
    removeFlag = False

    for token in tokenList:

        completionHash = aciServer.checkTaskForCompletion(token)

        # If the completion hash is not the empty hash, parse the information
        if completionHash != {}:
            # if we find that a task has completed, remove it from the list
            if completionHash['Status'] == 'FINISHED' and completionHash['Error'] == '':
                # The task completed successfully, remove the token from the list
                removeFlag = True

            elif completionHash['Status'] == 'RUNNING' and completionHash['Error'] == '':
                # The task must still be running
                print('Task ' + completionHash['Type'] + ' ' + token + ' has been running for ' + completionHash['Runtime'] + ' seconds.')

            elif completionHash['Status'] == 'queued':
                # The task is in the queue
                print('Task ' + completionHash['Type'] + ' ' + token + ' is queued in position ' + completionHash['QueuePosition'])

            elif completionHash['Status'] == 'not_found':
                # Did not find a task with this token, possible the task hasn't been added yet
                print(completionHash['Error'])

            # if the task is still running, no change to the token list will have occured

        else:
            # This is probably because the server got rid of the token after the task completed
            print('Completion hash is empty, something went wrong.')

            tokenListError.append(token)
            removeFlag = True

        if not removeFlag:
            print('appending token to updatedTokenList')
            updatedTokenList.append(token)


    print('length of tokenList after removal loop: ' + str(len(updatedTokenList)))

    # wait some time, proportional to the number of tasks left
    checkInterval = len(updatedTokenList) * checkIntervalMultiplier

    print('Waiting ' + str(checkInterval) + ' seconds before checking again...')
    print('Tokens remaining: ' + str(len(updatedTokenList)))

    # replace the original token list with the updated token list
    tokenList = updatedTokenList

    # wait a while based on how many tokens remain
    time.sleep(checkInterval)

所以这一切的重点是用新列表更新tokenList。每次循环中，新任务都将完成，不应将它们添加到updatedTokenList中。剩余的任务令牌将替换原始令牌列表。在

这不起作用。在我第一次传递时，它不会向updatedTokenList添加任何标记，即使还没有完成任何任务。我不知道我做错了什么。有什么建议吗？在

Answer 1

一个问题是，在removeFlag第一次遇到应该删除的标记之后，永远不会将其设置为False。一旦它检测到一个应该删除的标记，它也将从列表中删除该标记之后的所有标记。您需要在所有completionHash elif中将其设置为False（并确保它们测试的状态值是唯一可能的），或者直接在for token in tokenlist循环中设置它。在

如果在您的测试中，第一个作业在您第一次检查完成时已经完成，那么这将与所描述的行为相匹配。在