Enchancement suggestion for argparse: intuit type from default
roy at panix.com
Wed Mar 14 14:30:45 CET 2012
In article <87399bgw18.fsf at benfinney.id.au>,
Ben Finney <ben+python at benfinney.id.au> wrote:
> Right. I dislike proposals for run-time type inference in Python, since
> they are too magical.
> Especially since we're talking about user input (arguments from the
> command line to the program); that requires more explicit declarations
> and checking, not less.
> > What if you want an argument --foo that will accept arbitrary types? Then
> > you would need some way to tell argparse not to infer the type from the
> > default.
> So we would then need to special-case the special-case? Even more reason
> to dislike this proposal.
> > Explicit declarations should be used only for the uncommon cases where
> > type inference cannot cope.
> That's our point of disagreement, then: I think explicit declarations
> should be required regarding user input.
I wasn't suggesting that the type be inferred from what the user
entered. I was suggesting it be inferred from what the programmer had
done (i.e. what value they had given the 'default' parameter).
It's already inferred that the type is a string if you don't give it any
value. What possible meaning could:
have? If I run the program with:
then foo defaults to the integer 100, but if I run it with:
$ prog --foo=100
then I get the string "100"? Surely there's not much of a use case for
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