Function to apply superset of arguments to a function

[David Stanek]

On Wed, Sep 9, 2009 at 5:03 PM, Mel<mwilson at the-wire.com> wrote:
> David Stanek wrote:
>> On Wed, Sep 9, 2009 at 12:45 PM, Andrey Fedorov<anfedorov at gmail.com>
>> wrote:
>
>>> I've written a function [1] called apply_some which takes a set of
>>> keywords arguments, filters only those a function is expecting, and
>>> calls the function with only those arguments. This is meant to
>>> suppress TypeErrors - [ ... ]
>
>> What is your use-case for using this? It seems really odd to me.
>
> I may have run into one possible use.  I have a program that uses DB-API 2.0
> to work with a database, sometimes SQLite3, sometimes PostgreSQL.  Connect
> parameters are built up in a dict from a combination of defaults,
> environment values, and command-line arguments.  This dictionary has to be
> pruned down before calling connect, because sqlite3.connect doesn't take the
> wide assortment of arguments that are needed for PostgreSQL.  The existing
> program does this "by hand", being programmed in advance to know which
> parameters are acceptable to which database module.
>

The way I would normally do it is to use the URI format and based on
the scheme choose a handler. For example: mysql://user@host:server/db,
would translate to a mysql specific function that knows what to do.
Adding support for new schemes does mean an additional function, but I
like the control. And it's explicit.

I worry about the magic of the OP's approach. In your example generate
a dictionary in a generic way and apply it to a set of functions. What
happens if in the future if connect_mysql adds adds a parameter with
the same name as one in connect_postgres, but different semantics. Now
the magic is broken and you have an ugly special case.


-- 
David
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