[Tutor] Pseudo-functions and dicts

Kent Johnson kent37 at tds.net
Sat Mar 22 13:38:02 CET 2008

Shrutarshi Basu wrote:

> There are two solutions I've thought about:
> Have a function that takes in the sensor's name as a string and
> responds accordingly. (which might be what I'll end up using)

That is almost the same as using ordinary dict access, with slightly 
different syntax, e.g. sensor('sens1') vs sensor['sens1'].

There is actually a function to do this, it is called 
sensor.__getitem__. You can give it a new name if you like:

In [1]: sensor = {'sens1': 200, 'sens2': 300}
In [2]: get_value = sensor.__getitem__ # Note no parentheses here
In [3]: get_value('sens1')
Out[3]: 200

> I could let the user directly access the dict, but I'm not sure if
> that is a good idea. 

Why not?

> My project requires that the user of my module
> should not have to know about Python's data structures to use the
> values my module returns. 

This seems a strange requirement!

> If there is some sort of non-functional
> dot-separated syntax that I could use, that would be good too.

You could make a class whose attributes are the dict keys, then use 
attribute access syntax. The Bunch class is handy for this:

In [5]: values = Bunch(**sensor) # use sensor as keyword arguments
In [6]: values.sens1
Out[6]: 200


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