Enchancement suggestion for argparse: intuit type from default

Cameron Simpson cs at zip.com.au
Thu Mar 15 11:35:03 CET 2012

On 15Mar2012 10:06, Robert Kern <robert.kern at gmail.com> wrote:
| On 3/15/12 5:59 AM, Cameron Simpson wrote:
| > On 15Mar2012 12:22, Ben Finney<ben+python at benfinney.id.au>  wrote:
| > | Roy Smith<roy at panix.com>  writes:
| > |>  I'll admit I hadn't considered that, but I don't see it as a major
| > |>  problem. The type intuition could be designed to only work for types
| > |>  other than NoneType.
| > |
| > | −1, then. It's growing too many special cases, and is no longer simple
| > | to describe, so that indicates it's probably a bad idea.
| >
| > If `type` is not supplied and `default` is present and not None, `type`
| > shall be the type of `default`.
| >
| > That seems straightforward to me. [... sentinels aside...] the `type`
| > should always match type(default). Or am I wrong about that?
| Yes. Not all type(default) types can be called with a string to produce a valid 
| value. Note that "type=" is really a misnomer. argparse doesn't really want a 
| type object there; it wants a converter function that takes a string to an object.

Aha. Still, you could change the docs to say you only need type= if
type(default) _isn't_ useful as the string->value converter.
Cameron Simpson <cs at zip.com.au> DoD#743

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