Formalized pretty & encoding-aware object representation (was dunder methods for...)
Based on the conversations stemming from my previous post, it is clear that the topic was too implementation-specific. It is not clear whether dunder methods are an appropriate component of the solution (they might or might not be). Also, it presumably makes sense to start by looking at prior art rather than inventing from scratch. Quotes from previous thread regarding prior art to look at: Jonathan Fine wrote: <snip>
Alex Hall wrote:
Might be helpful to look at https://github.com/tommikaikkonen/prettyprinter and https://github.com/wolever/pprintpp
Steve Jorgensen wrote:
There has been some argument regarding whether objects should say how to present themselves "prettily". I think a case can be made either way, but in either case, it makes sense that it should be easy to override the representation for an object type without subclassing or monkey-patching it. Also, it might make sense not to clutter up the dunder-method space for all kinds of objects with this kind of thing. Without using dunder methods, it could still be possible for any body of code to provide default special-representational rules for its objects by registering hooks. Also, as a hybrid-approach, it could be that the defaults for representation are determined first by looking at a default registry and then falling back to dunder methods if present.
On 3/16/2020 1:15 PM, Steve Jorgensen wrote:
Which a singledispatch default handler could do. ========================== from functools import singledispatch @singledispatch def pretty(arg): try: fn = arg.pretty except AttributeError: return f"pretty default {arg}" return fn() @pretty.register(int) def _(arg): return f"pretty int {arg}" class HasPretty: def pretty(self): return "custom pretty function" print(pretty(1)) print(pretty(object)) print(pretty('a string')) print(pretty(HasPretty())) ========================== produces: ========================== pretty int 1 pretty default <class 'object'> pretty default 'a string' custom pretty function ========================== Just add arguments if desired and change the names as necessary. Eric
Steve Jorgensen wrote:
There has been some argument regarding whether objects should say how to present themselves "prettily". I think a case can be made either way, but in either case, it makes sense that it should be easy to override the representation for an object type without subclassing or monkey-patching it. Also, it might make sense not to clutter up the dunder-method space for all kinds of objects with this kind of thing. Without using dunder methods, it could still be possible for any body of code to provide default special-representational rules for its objects by registering hooks. Also, as a hybrid-approach, it could be that the defaults for representation are determined first by looking at a default registry and then falling back to dunder methods if present.
On 3/16/2020 1:15 PM, Steve Jorgensen wrote:
Which a singledispatch default handler could do. ========================== from functools import singledispatch @singledispatch def pretty(arg): try: fn = arg.pretty except AttributeError: return f"pretty default {arg}" return fn() @pretty.register(int) def _(arg): return f"pretty int {arg}" class HasPretty: def pretty(self): return "custom pretty function" print(pretty(1)) print(pretty(object)) print(pretty('a string')) print(pretty(HasPretty())) ========================== produces: ========================== pretty int 1 pretty default <class 'object'> pretty default 'a string' custom pretty function ========================== Just add arguments if desired and change the names as necessary. Eric
participants (2)
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Eric V. Smith -
Steve Jorgensen