[Python-ideas] Dict-like object with property access

Terry Reedy tjreedy at udel.edu
Thu Jan 26 22:28:06 CET 2012

On 1/26/2012 12:38 PM, Mike Meyer wrote:
> On Thu, 26 Jan 2012 19:25:40 +0200
> anatoly techtonik<techtonik at gmail.com>  wrote:

>> How about adding a new standard dict-like container type that allows
>> access using . (dot) to its members instead of ['index']?

We already have them: any subclass of *object*.

 >>> class Option: pass

 >>> options = Option
 >>> options.help = 'be happy'
 >>> options.help
'be happy'

Or did you mean 'instead of' to mean 'in addition to'?
That is actually possible too.
 >>> options.__dict__['help']
'be happy'
 >>> options_d = options.__dict__ # dict view of options
 >>> options.bye = 'Nice to know you!'
 >>> options_d['bye']
'Nice to know you!'

>> Why? It is convenient to write options.help instead of
>> options['halp'] etc.
> Because it doesn't work in general. There are strings that can be used
> as an index, but not as an attribute. There are existing attributes
> that you have to avoid, etc.
> The only way this really works in practice is if you start with a
> fixed set of names you want to access, in which case
> collections.namedtuple will probably do the job.

An advantage of collections.namedtuple is that all the pre-existing 
attributes start with '_' so as to avoid name clashes. Another is that 
name subscripts do *not* work, so there is no ambiguity there either.

Terry Jan Reedy

More information about the Python-ideas mailing list