Adaptation and typecasting (was Re: [Python-Dev] replacing 'global')

Greg Ewing greg at
Tue Oct 28 21:56:53 EST 2003

"Phillip J. Eby" <pje at>:

> Given all this, I think I'm okay with saying that adapting from a mutable 
> object to an immutable interface (e.g list->tuple) is an improper use of 
> adaptation.

Expecting such an adaptation to somehow make the underlying
list unchangeable by any means would be unreasonable, I
think. I can't see any way of enforcing that other than by
making a copy, which goes agains the spirit of adaptation.

There still might be uses for it, though, without any
unchangeability guarantee, such as passing it to something
that requires a tuple and not just a sequence, but not
wanting the overhead of making a copy.

Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury,	   | A citizen of NewZealandCorp, a	  |
Christchurch, New Zealand	   | wholly-owned subsidiary of USA Inc.  |
greg at	   +--------------------------------------+

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