[Python-Dev] Iterable String Redux (aka String ABC) (original) (raw)

Guido van Rossum guido at python.org
Tue May 27 21:42:48 CEST 2008

[+python-3000]

On Tue, May 27, 2008 at 12:32 PM, Armin Ronacher <armin.ronacher at active-4.com> wrote:

Strings are currently iterable and it was stated multiple times that this is a good idea and shouldn't change. While I still don't think that that's a good idea I would like to propose a solution for the problem many people are experiencing by introducing an abstract base class for strings.

Basically the problematic situation with iterable strings is something like a flatten function that flattens out every iterable object except of strings. Imagine it's implemented in a way similar to that:: def flatten(iterable): for item in iterable: try: if isinstance(item, basestring): raise TypeError() iterator = iter(item) except TypeError: yield item else: for i in flatten(iterator): yield i A problem comes up as soon as user defined strings (such as UserString) is passed to the function. In my opinion a good solution would be a "String" ABC one could test against.

I'm not against this, but so far I've not been able to come up with a good set of methods to endow the String ABC with. Another problem is that not everybody draws the line in the same place -- how should instances of bytes, bytearray, array.array, memoryview (buffer in 2.6) be treated?

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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