[Python-Dev] Tuples vs. lists

[Aahz Maruch]

Guido van Rossum wrote:
> Aahz:
>>
>> Hrm.  Even when it's something that's supposed to be immutable?  I'm
>> asking because I'm currently using a tuple for the digit list in my BCD
>> module, and I'd like a clearer explanation of why you think that it
>> should be a list (assuming you do).
>> 
>> From my viewpoint, the BCD digit string should be handled like a string;
>> I'm only using a tuple for efficiency of storing numbers instead of
>> characters.
> 
> Can't you trust your users not to change it?

Sure, but then I can't just copy references to the tuple when creating a
copy of an instance, I'd have to copy the entire list.  That's what I
meant by efficiency.  There are important semantic differences coming
from the fact that tuples are immutable and lists are mutable, and I
think that a strict heterogeneous/homogenous distinction loses that.
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