處理最大遞歸深度超過

Question

我創建了一個使用遞歸來解決簡單迷宮的程序。在迷宮相當複雜的情況下，我會得到最大的遞歸深度誤差。我在這個網站上搜索了這個錯誤並閱讀了主題，所以我相信我對發生的事情有了一個大概的瞭解。

與我看到的其他線程不同，我並不試圖增加遞歸限制。 sys.setrecursionlimit（）不是我正在尋找的。我想能夠處理溢出，而不是崩潰程序打印一條消息（print("Sorry but this maze solver was not able to finish analyzing the maze due to recursion limits)）並關閉。

我知道使用try和except來處理錯誤，但我不確定是否可以合併它來處理最大遞歸深度錯誤。

Answer 1

最大遞歸深度錯誤只是另一個例外;你可以趕上RecursionError exception（Python的3.5或更高版本）：

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

我已經納入連接到運行時異常錯誤信息;對於遞歸錯誤maximum recursion depth exceeded。

如果您需要支持3.5以前的Python版本，則可以捕獲基類RuntimeError。如果你擔心趕上那些不遞歸深度錯誤運行時錯誤，你可以內省.args[0]值：

try: 
    solveMaze(maze) 
except RuntimeError as re: 
    if re.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(re.args[0])) 

的選項演示：

>>> def infinity(): return infinity() 
... 
>>> try: 
...  infinity() 
... except RecursionError as re: 
...  print('Oopsie: {}'.format(re.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 re: 
...  print('Oopsie: {}'.format(re.args[0])) 
... 
Oopsie: dictionary changed size during iteration 
>>> try: 
...  infinity() 
... except RuntimeError as re: 
...  if re.args[0] != 'maximum recursion depth exceeded': 
...   raise 
...  print('Oopsie: {}'.format(re.args[0])) 
... 
Oopsie: maximum recursion depth exceeded 
>>> try: 
...  alter_dict_size() 
... except RuntimeError as re: 
...  if re.args[0] != 'maximum recursion depth exceeded': 
...   raise 
...  print('Oopsie: {}'.format(re.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 

改變一個字典大小也提出了一個RuntimeError異常，但測試生成的異常消息可以讓您區分。