[Patches] [ python-Patches-1696444 ] Adding an index method to tuples

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Patches item #1696444, was opened at 2007-04-08 09:35
Message generated for change (Comment added) made by rhettinger
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Paul Boddie (pboddie)
Assigned to: Nobody/Anonymous (nobody)
Summary: Adding an index method to tuples

Initial Comment:
This is just a simple copy and paste from the list implementation - not exactly the most elegant solution, but perhaps a demonstration that technical limitations aren't the reason why the tuple doesn't have an index method. I suppose a common sequence function library would be best if such a feature were eventually deemed compelling.

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>Comment By: Raymond Hettinger (rhettinger)
Date: 2007-04-09 15:41

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Adding a utility function for this is silly.  Don't ignore the obvious,
simple solution.  If a type *needs* a method, add it.  If not, don't. 

Also, the collecitons module should be about collections, not a dumping
ground for random utility functions.

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Comment By: Josiah Carlson (josiahcarlson)
Date: 2007-04-09 15:06

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I wouldn't be averse to adding utility functions to some module where it
would make sense.  Generally, I would say collections (it has a deque and
default dictionary already), though there is already a proposed constructor
called 'count' that returns the counts of all items in a sequence as a
default dictionary (requiring that the items all be hashable).

The reason I'm not against utility functions is because then they would be
usable for 3rd party non-list, non-tuple sequences, or even usable in cases
like 'a = array.array(...); i = index(a, value)'.

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Comment By: Paul Boddie (pboddie)
Date: 2007-04-09 14:51

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See here for a recent extension of the discussion:

http://groups.google.com/group/comp.lang.python/browse_frm/thread/7e9327a896c242e7/

For what it's worth, bypassing the dogma, methods like index and count on
tuples are not exactly compelling in many situations (as I've pointed out
before), but such issues should hardly derail the core development effort.
If people consider such methods useful and if it diminishes perceived
inelegance without method proliferation, just add them: people will be less
frustrated and feel listened to; the language will become more regular.

The only downside is any additional memory consumption. Objections related
to what such methods mean, or what a tuple itself should be taken to mean,
risk venturing into dogma and a consequent time-consuming discussion which
takes 100 times the effort of just getting stuff done. Just look at the
referenced thread (and the others of recent times) for example material.

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Comment By: Raymond Hettinger (rhettinger)
Date: 2007-04-09 12:08

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FWIW, I am no longer satisfied with the pat answer that "tuples are not
immutable lists" or the "lists for for homogenous data, tuples are for
hetrogenous data".

Whether tuples should grow index() and count() methods should depend
solely on whether real use cases arise often enough to warrant the new
methods being added.

Another consideration is that this feature request and discussion comes up
so often that it may be worthwhile just to give-in to conserve our limited
resources of time and brain-power.

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Comment By: Josiah Carlson (josiahcarlson)
Date: 2007-04-09 11:24

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Adding an .index method to tuples suggests that a tuple is more or less an
immutable list.  This is not the case.  Typically tuples are used to hold
disparate pieces of information of different semantics and types, where as
a list typically contains a list of a single type with identical meaning. 
For examples we merely need to look at the outputs of str.partition and
str.split .

Suggested close.

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