Thoughts about Python
PPNTWIMBXFFC at spammotel.com
Wed Feb 25 10:23:37 CET 2004
cookedm+news at physics.mcmaster.ca (David M. Cooke) wrote in message news:<qnk4qtgt7j9.fsf at arbutus.physics.mcmaster.ca>...
> At some point, PPNTWIMBXFFC at spammotel.com (Marco Aschwanden) wrote:
> >> Forget the speed and memory difference. The main argument for tuples as a
> >> separate type are to use as dictionary keys. How do you propose to handle
> >> dictionary keys without tuples?
> > Maybe I don't get the point here: Why do dictionaries need tuples to
> > work? I know that tuples can be used as keys... but how many times do
> > you need tuples as dictionary keys (it would be simple to turn a list
> > into an immutable string if really needed ("::".join(["a","b"]).
> Simple, yes. Practicable, no. Wrong, certainly. For instance, I have a
> lot of use cases where I use tuples of numbers -- (3, 4, 20.0101), eg.
> It'd be a *hack* to convert that into a string, and the representation
> would not be unique. This ain't Perl.
>>> tup = (3, 4, 20.0101)
>>> stringified = str(tup)
'(3, 4, 20.010100000000001)' # 8o)
What is not unique about this string?
Okay, I can think of cases where this approach is problematic -
foremost when sorting is involved.
It is also a bit complicated to retrieve the values from the string
(it has to be "split"ted or "eval"ed back to a tuple or list).
If this pattern would be seldom used... but it seems, that everybody
except me uses this dicts as keys.
And yes, luckily this is not Perl.
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