key - key pairs

[Terry Hancock]

On Thursday 23 June 2005 02:40 pm, Florian Lindner wrote:
> is there in python a kind of dictionary that supports key - key pairs?
> I need a dictionary in which I can access a certain element using two
> different keys, both unique.
> 
> For example:
> 
> I've a dictionary with strings and times. Sometimes I have the string and I
> want to have the time, other time I've the time and I want the string. It
> is important that one of the keys supports the min/max builtin function.

Well, really, you're always using one or the other as the "key" and the other
as the "value".  Furthermore, it is not in the general case assured that you
can do this --- the keys may not really be 1:1.

If you are content to restrict yourself to the 1:1 case, you can construct
an inverse dictionary from the first dictionary like this:

time2string = dict([ (b,a) for a,b in string2time.items() ])

Note that if string2time has duplicate values, this will arbitrarily pick
one (in a consistent, but implementation dependent way) to use as
the key in the inverse mapping.

--
Terry Hancock ( hancock at anansispaceworks.com )
Anansi Spaceworks  http://www.anansispaceworks.com