python bijection

[Raymond Hettinger]

> >   ...sqlite3 provides another way...
>
> In many many cases, using a dB (even a lightweight such as sqlite3) is
> swatting the fly with a sledgehammer :-)

I'm sure it seems that way, but look at the generic description of the
problem: "I have a list of n-ary tuples with named fields and would
like to be able to retrieve a tuple using any of m-fields as a lookup
key (where 2 <= m <= n).  Also, I would like to enforce the constraint
that those m-fields are all unique keys."

That pretty much sounds like a typical database problem featuring a
single table with multiple indexes.  One can wish-away the complexity
of a database but you will end-up re-inventing an in-memory, one-table
version of database.

===============
phonelist
===============
name   idnumber
----   --------
ray    1234
josh   5423
carl   8674
tery   5409
greg   3402
mark   2108

tasks
-----
list names
list idnumbers
find idnumber=2108
find name=greg
del  name=tery
update idnumber=4321 where name=ray
list sorted by name
list sorted by idnumber reversed
is name=john in phonelist
Now, extend the table to make it a trijection (three unique keys),
perhaps a social security number.
Now, extend the table to add a field that isn't unique (not a key
field), perhaps a person's favorite language.
Oh wait, you can't do that with a bijection API.
Now, forget the in-memory part and make it persistent on disk.
Now, relate the entries to another dictionary of tuples (i.e. another
table with foreign-key).
Too bad a DB wasn't used to solve a DB problem.


Raymond