Friday Finking: Limiting parameters

[Peter J. Holzer]

On 2020-07-13 17:21:40 +1200, dn via Python-list wrote:
> On 12/07/20 10:10 PM, Barry Scott wrote:
> > I'd expect to see something like this:
> > 
> > def mail_label( person, address ):
> > first_name = person.first_name
> > # or if you want a function interface
> > first_line_of_address = address.get_first_line()
> 
> Does this idea move whole objects across the interface? (see earlier in the
> thread)

Assigning an object in Python only copies a pointer (and may adjust some
house-keeping info, like a reference count). So it doesn't matter
whether the object  has 5 fields or 50. The function will only access
those it knows about and ignore the rest.

One might argue that mail_label should be a method of the person object
because it depends on the person (e.g., depending on the ethnicity of
the person the name might be written "first_name last_name" or
"last_name firstname"). OTOH a person may have many addresses (and an
address shared by many people), so a function which combines a person
and address (which therefore can't be a method of either person or
address) may be better. 

Maybe that should be treated as a model-view relationship: You have two
models (person and address) and a view (which combines some aspects of
both while ignoring others).

        hp

-- 
   _  | Peter J. Holzer    | Story must make more sense than reality.
|_|_) |                    |
| |   | hjp at hjp.at         |    -- Charles Stross, "Creative writing
__/   | http://www.hjp.at/ |       challenge!"
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