[Python-ideas] Python Users Aren't Perfect

Guido van Rossum guido at python.org
Fri Dec 16 02:39:04 CET 2011

On Thu, Dec 15, 2011 at 5:16 PM, Terry Reedy <tjreedy at udel.edu> wrote:

> On 12/15/2011 3:42 PM, Ned Batchelder wrote:
>  This is another place where Python is inconsistent. We're told, "lists
>> are for homogenous sequences of varying length, like a C array; tuples
>> are for heterogenous aggregations of known length, like a C struct."
> I have not been told that for several years, and I am pretty sure you will
> not find any such thing in the current docs. I consider it pretty much
> obsolete, as the differences that flowed from that idea are gone. In Python
> 3, tuples have all the non-mutating sequence methods that list does. The
> situation was much different in 1.4.

I strongly disagree. Being immutable sequences (i.e. homogeneous) is a
minor secondary role for tuples. Their primary role remains to hold a small
bunch of heterogeneous values -- like namedtuple, but without needing
forethought. A good example are dictionary items -- these are (key, value)
pairs where for a given dict, the keys are all of the same type (or of a
small set of related types) and ditto for the values, but the key type and
the value types are unrelated.

--Guido van Rossum (python.org/~guido)
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