Typing: RuntimeError: maximum recursion depth exceeded while calling a Python object

[Pitometsu]

v = 1
t = int
for _ in range(0, 1000):
    v = (1, v, 1)
    t = tp.Tuple[int, t, int]
e = (v, t)
print e

Traceback (most recent call last):
  File "/Users/netsu/.virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 2882, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-174-01b42d124d17>", line 5, in <module>
    t = tp.Tuple[int, t, int]
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 754, in inner
    value = func(*args)
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 1374, in __getitem__
    return super(TupleMeta, self).__getitem__(parameters)
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 754, in inner
    value = func(*args)
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 1254, in __getitem__
    orig_bases=self.__orig_bases__)
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 1113, in __new__
    self.__tree_hash__ = (hash(self._subs_tree()) if origin else
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 1197, in _subs_tree
    tree_args = _subs_tree(self, tvars, args)
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 675, in _subs_tree
    tree_args.append(_replace_arg(arg, tvars, args))
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 634, in _replace_arg
    return arg._subs_tree(tvars, args)
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 1197, in _subs_tree
    tree_args = _subs_tree(self, tvars, args)
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 675, in _subs_tree
    tree_args.append(_replace_arg(arg, tvars, args))
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 634, in _replace_arg
    return arg._subs_tree(tvars, args)
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 1197, in _subs_tree
    tree_args = _subs_tree(self, tvars, args)


 . . .

  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 675, in _subs_tree
    tree_args.append(_replace_arg(arg, tvars, args))
  File "/Users/netsu/.local/share/virtualenvs/csr-44kfYsMA/lib/python2.7/site-packages/typing.py", line 635, in _replace_arg
    if isinstance(arg, TypeVar):
RuntimeError: maximum recursion depth exceeded while calling a Python object

[Pitometsu]

Slouldn't recursion be avoided here because of python's lack of tail recursion optimization and use any of: iteration, continuations, stack machine, exceptions, etc.?

[Pitometsu]

With just value – everything fine

v = 1
for _ in range(0, 1000):
    v = (1, v, 1)
print v
(1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, (1, 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1)

[Pitometsu]

https://github.com/python/typing/blob/master/python2/typing.py#L635

[JelleZijlstra]

Is there a practical use case for your example? Printing deeply recursive data structures will naturally require recursion, even if there are shortcuts for built-in datatypes like tuples.

[ilevkivskyi]

I don't think we should sacrifice (already limited) clarity of code to save call stack consumption for this very rare situation. (Also it will be already consumed less in Python 3.7 with PEP 560). For your things just use sys.setrecursionlimit(<something large>).

[Pitometsu]

@ilevkivskyi you can use something like https://github.com/baruchel/tco as decorator to keep relative clarity. It just need to be rewritten as tail recursion to be safe.
Would you accept PR?

[Pitometsu]

Unfortunately, I can't just enhance stack size, because it need to be checked that my code work with any stack size, and for now it sadly limited by typing implementation.

[Pitometsu]

@JelleZijlstra practical reason is to cover by typing expressions that actually can exist in python (as you see in example, they are not limited by stack size).

[ilevkivskyi]

Would you accept PR?

I am not against a PR with a tail call optimization, but I am quite sure @gvanrossum will be against TCO.

[Pitometsu]

I'm about PR with rewriting recursion to something that doesn't overflowing stack. To keep code clarity, it can emulate pseudo-recursion by doing necessary transformations to loop/continuation/stack machine in decorator. Mentioned before https://github.com/baruchel/tco as exist example. Actually, python, as a script language, lack ability to have real TCO by design, you right. But it doesn't really need the real recursion to keep code clean and free of stack overflow bombs. It have decorators. Anyway, issue isn't solved, could you reopen it, please – in case if someone would have ideas how to solve it in elegant way?

[gvanrossum]

I'm not interested in this kind of transformation.

On Dec 28, 2017 7:27 AM, "Yuriy Pitomets" [e-mail] wrote:

I'm about PR with rewriting recursion to something that doesn't
overflowing stack. To keep code clarity, it can emulate pseudo-recursion by
doing necessary transformations to loop/continuation/stack machine in
decorator. Mentioned before https://github.com/baruchel/tco as exist
example. Actually, python, as an script language, lack ability to have real
TCO by design, you right. But it doesn't really need the real recursion to
keep code clean and free of stack overflow bombs. It have decorators.
Anyway, issue isn't solved, could you reopen it, please – in case if
someone would have ideas how to solve it in elegant way?

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[Pitometsu]

@gvanrossum did you even read the topic? Is stack overflow ok for you?

[o1dnik]

That's a topic...
1 http://neopythonic.blogspot.cz/2009/04/tail-recursion-elimination.html
2 http://www.kylem.net/programming/tailcall.html
again, you may initiate your own BDFLism by implementing it your own way

[gvanrossum]

My comment was not for you. It was to let other devs on typing know that
they don't have to continued this thread.

On Dec 28, 2017 2:51 PM, "nikita" [e-mail] wrote:

That's a topic...
1 http://neopythonic.blogspot.cz/2009/04/tail-recursion-elimination.html
2 http://www.kylem.net/programming/tailcall.html
again, you may initiate your own BDFLism by implementing it your own way

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[cegprakash]

I still have this issue

[Pitometsu]

@cegprakash it's Python: nobody cares.

[liuming5467]

import sys
sys.setrecursionlimit(100000)

[naazneen]

import sys
sys.setrecursionlimit(100000)

Where do you write this? in spec file?