在 Python/django 中读取 json 时可能出现多少异常？

Question

我有：

MY_PATH_DIR = 'path/to/my/json/file.json'

try:
    with open(MY_PATH_DIR, 'r') as f:
        MY_PATH_DIR = json.load(f)
except IOError, RuntimeError, ValueError:
    pass
except PermissionDenied:
    pass

我想捕捉所有可能的错误。与

• IOError - 当文件不存在或有 语法错误（无效的 JSON）。

• RuntimeError - 无法测试，但我认为从 发生意外错误时的文档

• ValueError - 我从here 收到以防万一没有返回

• PermissionDenied - 是特定的 Django 错误

还有其他有意义的例外吗？我不确定OSError 在这里是否有意义。我认为这会更早提出，对吧？

Answer 1

import random
import sys


def main():
    """Demonstrate the handling of various kinds of exceptions."""
    # This is like what you are doing in your code.
    exceptions = IOError, RuntimeError, ValueError
    try:
        raise random.choice(exceptions)()
    except exceptions as error:
        print('Currently handling:', repr(error))
    # The following is not much different from Shang Wang's answer.
    try:
        raise random.choice(exceptions)()
    except Exception as error:
        print('Currently handling:', repr(error))
    # However, the following code will sometimes not handle the exception.
    exceptions += SystemExit, KeyboardInterrupt, GeneratorExit
    try:
        raise random.choice(exceptions)()
    except Exception as error:
        print('Currently handling:', repr(error))
    # The code can be slightly altered to take the new errors into account.
    try:
        raise random.choice(exceptions)()
    except BaseException as error:
        print('Currently handling:', repr(error))
    # This does not take into account classes not in the exception hierarchy.
    class Death:
        pass
    try:
        raise Death()
    except BaseException as error:
        print('Currently handling:', repr(error))
    # If your version of Python does not consider raising an exception from an
    # instance of a class not derived from the BaseException class, the way to
    # get around this problem would be with the following code instead.
    try:
        raise Death()
    except:
        error = sys.exc_info()[1]
        print('Currently handling:', repr(error))


if __name__ == '__main__':
    main()

Answer 2

捕获异常的目的是控制程序在发生不好的事情时的行为，但以预期的方式。如果您甚至不确定导致该异常发生的原因，那么捕获它只会吞噬您可能遇到的底层编程错误。

我不会在单个代码块中添加尽可能多的异常，您应该只添加您关心的内容。更极端地说，每一行代码都会产生某些异常，但出于显而易见的原因，您不能对所有异常都执行try except。

编辑：

为了正确起见，既然您在任何情况下都提到了I don't want my code to break，您可以简单地这样做：

try:
    # json.load
except Exception as e:
    print "Let's just ignore all exceptions, like this one: %s" % str(e)

这将为您提供作为输出发生的异常情况。