尝试添加错误处理机制时出现“ Continue not in loop”错误

如何解决尝试添加错误处理机制时出现“ Continue not in loop”错误

我一直在尝试向我的代码部分添加错误处理机制。但是，当它运行时，它说“在循环外继续”，但查看代码，它应该在try循环内。怎么了？

def download_media_item(self,entry):
    try:
        url,path = entry
        # Get the file extension example: ".jpg"
        ext = url[url.rfind('.'):]
        if not os.path.isfile(path + ext):
            r = requests.get(url,headers=headers,timeout=15)
            if r.status_code == 200:
                open(path + ext,'wb').write(r.content)
                self.user_log.info('File {} downloaded from {}'.format(path,url))
                return True
            elif r.status_code == 443:
                print('------------the server reported a 443 error-----------')
                return False
        else:
            self.user_log.info('File {} already exists. URL: {}'.format(path,url))
            return False
    except requests.ConnectionError:
        print("Received ConnectionError. Retrying...")
        continue
    except requests.exceptions.ReadTimeout:
        print("Received ReadTimeout. Retrying...")
        continue   

解决方法

continue是专门，用于立即移至for或while循环的下一个迭代；这不是通用的“移至下一个语句”指令。

在try / except语句中，只要到达try，except，else或finally块的末尾，则执行从下一个complete语句而不是try语句的下一部分开始。

def download_media_item(self,entry):
    # 1: try statement
    try:
        ...
        # If you get here,execution goes to #2 below,not the
        # except block below
    except requests.ConnectionError:
        print("Received ConnectionError. Retrying...")
        # Execution goes to #2 below,not the except block below
    except requests.exceptions.ReadTimeout:
        print("Received ReadTimeout. Retrying...")
        # Execution goes to #2 below

    # 2: next statement
    ...

,

似乎您实际上想要做的是保持循环，直到没有异常出现为止。

通常，您可以通过在成功完成时中断无限循环来做到这一点。

要么：

while True:
    try:
        # do stuff
    except requests.ConnectionError:
        # handle error
        continue
    except requests.exceptions.ReadTimeout:
        # handle error
        continue
    break

或者：

while True:
    try:
        # do stuff
    except requests.ConnectionError:
        # handle error
    except requests.exceptions.ReadTimeout:
        # handle error
    else:
        break

但是，在这种情况下，“做事”似乎总是以到达return语句结束，因此不需要break，并且以下简化版本就足够了：

while True:
    try:
        # do stuff
        return some_value
    except requests.ConnectionError:
        # handle error
    except requests.exceptions.ReadTimeout:
        # handle error

（如您所见，此处显示的单个return可能是指替代控制流，所有这些控制流都导致一个return。）