Re: dictionaries?

• To: mathgroup at smc.vnet.net
• Subject: [mg20608] Re: dictionaries?
• From: "John M. Jowett" <John.Jowett at cern.ch>
• Date: Thu, 4 Nov 1999 02:13:27 -0500
• Organization: CERN
• References: <7v3bov\$5tg@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Joe Strout wrote:
>
> In Python, there's an extremely handy datatype called a "dictionary"
> which implements a many-to-1 mapping between keys (which can be any
> hashable type) and values (which can be anything).  E.g.:
>
> > d = {"one":1, "two":2}
> > d["one"]
> 1
> > d["three"]
> (key not found)
>
> I'm looking for something similar in Mathematica

Depending on exactly what you want to do, Mathematica's rules may be fit
the bill, e.g., define a named set of rules

d = {one->1,two->2}

then you can have things like

In[6]:=
x[one] /. d

Out[6]=
x[1]

In[8]:=
two + three /. d

Out[8]=
2 + three

Rules are often a handy one to store a set of substitutions.

John Jowett
--
----------------------------------------------------------------------
My home page:    http://wwwslap.cern.ch/~jowett/
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