Why I get RecursionError on very small amount of data?

[wavic]

I can't imagine how is possible to get this error when I use the function on such a small data
How is that even possible?

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In [1]: l = [list(word) for word in 'Something goes wrong'.split()]   In [2]: def flatten(iterable):    ...:     iterator = iter(iterable)    ...:     for item in iterator:    ...:         if '__iter__' in dir(item):    ...:             yield from flatten(item)    ...:         else:    ...:             yield item    ...:               In [3]: flat = [item for item in flatten(l)]   --------------------------------------------------------------------------- RecursionError                            Traceback (most recent call last) <ipython-input-3-930115f14cc4> in <module>() ----> 1 flat = [item for item in flatten(l)]   <ipython-input-3-930115f14cc4> in <listcomp>(.0) ----> 1 flat = [item for item in flatten(l)]   <ipython-input-2-7311442c70ce> in flatten(iterable)       3     for item in iterator:       4         if '__iter__' in dir(item): ----> 5             yield from flatten(item)       6         else:       7             yield item   ... last 1 frames repeated, from the frame below ...   <ipython-input-2-7311442c70ce> in flatten(iterable)       3     for item in iterator:       4         if '__iter__' in dir(item): ----> 5             yield from flatten(item)       6         else:       7             yield item   RecursionError: maximum recursion depth exceeded while calling a Python object   In [4]:   In [4]: flat = [item for item in flatten(l)] --------------------------------------------------------------------------- RecursionError                            Traceback (most recent call last) <ipython-input-4-930115f14cc4> in <module>() ----> 1 flat = [item for item in flatten(l)]   <ipython-input-4-930115f14cc4> in <listcomp>(.0) ----> 1 flat = [item for item in flatten(l)]   <ipython-input-2-7311442c70ce> in flatten(iterable)       3     for item in iterator:       4         if '__iter__' in dir(item): ----> 5             yield from flatten(item)       6         else:       7             yield item   ... last 1 frames repeated, from the frame below ...   <ipython-input-2-7311442c70ce> in flatten(iterable)       3     for item in iterator:       4         if '__iter__' in dir(item): ----> 5             yield from flatten(item)       6         else:       7             yield item   RecursionError: maximum recursion depth exceeded while calling a Python object   In [5]:

[micseydel]

Without having dug into it, I would imagine it's because your base case is characters, which are length-1 strings, which are iterable. I expect it would work if the smallest elements are scalars (e.g int).

[wavic]

Hm! I have tried it with integers and it worked. It's strange to me.
sys.getrecursionlimit() says that it is 1000.
How it happens if an element is a string ( iterable) this limit is reached? This is not happening during code execution I suppose.

[micseydel]

How it happens if an element is a string ( iterable) this limit is reached?

Output:
>>> '__iter__' in dir('c')
True