python - 处理超过最大递归深度

Question

我创建了一个使用递归来解决简单迷宫的程序。如果遇到相当复杂的迷宫，我会得到最大递归深度错误。我已经在该网站上搜索了该错误并阅读了线程，所以我相信我对发生的事情有一个大致的了解。

与我看到的其他线程不同，我没有尝试增加递归限制。 sys.setrecursionlimit() 不是我要找的。我希望能够处理溢出，而不是崩溃让程序打印一条消息(print(“抱歉，由于递归限制，这个迷宫求解器无法完成分析迷宫))并关闭。

我知道使用 try 和 except 来处理错误，但我不确定我是否可以合并它来处理最大递归深度错误。

Answer 1

最大递归深度错误只是另一个异常(exception)；你可以 catch RecursionError exception (Python 3.5 或更高版本):

try:
    solveMaze(maze)
except RecursionError as err:
    print('Sorry but this maze solver was not able to finish '
          'analyzing the maze: {}'.format(err.args[0]))

我已经合并了附加到运行时异常的错误消息；对于 maximum recursion depth exceeded 的递归错误。

如果需要支持3.5之前的Python版本，可以抓到基类，RuntimeError .如果您担心捕获不是递归深度错误的运行时错误，您可以内省(introspection).args[0] 值:

try:
    solveMaze(maze)
except RuntimeError as err:
    if err.args[0] != 'maximum recursion depth exceeded':
        # different type of runtime error
        raise
    print('Sorry but this maze solver was not able to finish '
          'analyzing the maze: {}'.format(err.args[0]))

选项演示:

>>> def infinity(): return infinity()
... 
>>> try:
...     infinity()
... except RecursionError as err:
...     print('Oopsie: {}'.format(err.args[0]))
... 
Oopsie: maximum recursion depth exceeded
>>> def alter_dict_size():
...     dct = {'foo': 'bar'}
...     for key in dct:
...         del dct['foo']
... 
>>> try:
...     alter_dict_size()
... except RuntimeError as err:
...     print('Oopsie: {}'.format(err.args[0]))
... 
Oopsie: dictionary changed size during iteration
>>> try:
...     infinity()
... except RuntimeError as err:
...     if err.args[0] != 'maximum recursion depth exceeded':
...         raise
...     print('Oopsie: {}'.format(err.args[0]))
... 
Oopsie: maximum recursion depth exceeded
>>> try:
...     alter_dict_size()
... except RuntimeError as err:
...     if err.args[0] != 'maximum recursion depth exceeded':
...         raise
...     print('Oopsie: {}'.format(err.args[0]))
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "<stdin>", line 3, in alter_dict_size
RuntimeError: dictionary changed size during iteration

改变字典大小也会引发 RuntimeError 异常，但测试生成的异常消息可以让您区分。