Re: type(foo) == function ?

On 11/29/06, Tom Plunket <tomas@xxxxxxxxx> wrote:
Erik Max Francis wrote:

> In dynamically-typed languages in general, explicit typechecks are not
> a good idea, since they often preclude user-defined objects from being
> used. Instead, try performing the call and catch the resulting
> TypeError:

Good point, although I need to figure out if the thing can be called
without calling it, so I can build an appropriate UI. Basically I
expect three types of things in the 'value' field of the top-level
dictionary. The three sorts of things that I will deal with in the UI
are callable things (e.g. functions, for which Chris Mellon reminds me
about callable()), mappings (e.g. dictionaries, used similarly to the
top-level one), and sequences of strings.

So I think callable() works for me in the general case, but now
trawling the documentation in that area I'm not sure how I can tell if
something is a mapping or if it's a sequence.

The gist of the UI generation may be envisioned as:

key is the name that gets assigned to the control.
value indicates that the UI element is a:
"group box" if the value is a mapping
series of "radio buttons" if the value is a sequence of strings
"check box" if the value is a function

...I've still gotta figure out the exact API, this is for a plugin
sort of system that'll be used by the manually-driven version of the
build process and this data is explicitly to build the UI for the
various tools that are available.


Since a sequence can be viewed as a special case of a mapping (a dict
with integer keys) I don't think there's a good general case way to
tell.

You could try indexing it with a string, a sequence will throw a
TypeError, while a mapping will give you a result or a KeyError.

You could also just rely on isinstance() checks.

thanks,
-tom!
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