WENDUM Denis 47.76.11 (agent) wrote:
> While testing recursive algoritms dealing with generic lists I stumbled
> on infinite loops which were triggered by the fact that (at least for my
> version of Pyton) characters contain themselves.See session:
Strings are sequences and this is a problem for recursive functions that
process nested lists. You do need to test for stringiness somehow. IIRC
the usual solutions are
- explicit test for string: isinstance(xx, basestring)
- explicit test for list: isinstance(xx, list) - this fails for
user-defined sequences that don't subclass list
- test for __iter__ attribute. IIUC this relies on an implementation
detail that strings don't define __iter__:
In [6]: hasattr('aa', '__iter__')
Out[6]: False
In [7]: hasattr([], '__iter__')
Out[7]: True
Kent
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