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Comment by westandskif | Hacker News Reader

oh, thanks, I'll add links to cheatsheet and quickstart pages to the README, it really makes sense!

As for the magic-stuff, I was contemplating designing the API with this approach, but I changed my mind because it would be difficult to tell which python expressions are evaluated at the moment of a conversion definition AND which in the compiled code.

However if we imagine this "magic" API, then it could be even closer to normal python code:

  m["key"].some_method(...)

which would resolve everything under the hood.

===

as for the collapsable generated code examples -- I've jotted down :)

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> it would be difficult to tell which python expressions are evaluated at the moment of a conversion definition AND which in the compiled code

this is ofc a valid concern in any metaprogramming situation. has this been a problem in your experience? i'm guessing e.g. generating a conversion based on a list of fields is a thing someone might do, but it feels like a minority usecase (at least to me, someone with no actual experience with using the library :p)

Re: whether it's been a problem in my experience -- sort of - yes

So now I'm doing my best to observe: PEP-20 the 2nd commandment with the hope that I'm not violating the 1st commandment badly :) https://www.python.org/dev/peps/pep-0020/

Also I see another upside of this no-magic syntax in that it is distinctive -- there's no way to mix up convtools-related code with any other python code.

In re: the "magic", it seems to me that you could use a mock object and get the required info from it.

In terms of the implementation, it's kind of trivial to implement the "magic", but it would be both confusing and inconsistent, see below.

e.g. imagine a case where you'd want to call datetime.strptime, partially initializing it at the moment of conversion definition. at the moment it is:

  c.call_func(
      datetime.strptime,
      c.item("updated"),
      "%Y-%m-%d"
  )

but it's unclear to me how would the "magic" approach deal with the case above.

Replace your current namespace with a mock object? You can eval or exec code with any dictionary-flavored object, and mocks can imitate dicts.

edit: no, you can't in Python 3..

I'll try to have a closer look later today.

What do you think about a DSL alternative?

We would need to bring the whole python into it :/

looks really cool -- will evaluate when the API is stable -- would hate to adopt only to have it change from under me

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