Question

try:
    recursive_function()
except RuntimeError e:
    # is this a max. recursion depth exceeded exception?

How do I tell when the maximum recursion depth has been reached?

Answer 1

You can look inside the exception itself:

>>> def f():
...     f()
... 
>>> try:
...     f()
... except RuntimeError as re:
...     print re.args, re.message
... 
('maximum recursion depth exceeded',) maximum recursion depth exceeded

I don’t think you can distinguish between this and something merely pretending to be a recursion-depth-exceeded (Runtime) exception, though. message is deprecated, so args is probably the best bet, and is Python-3 compatible.

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Update: in Python 3.5, there’s a specific RecursionError which you can catch instead.