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Avro, mail # dev - Python-Avro Codegen Proposal


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Tal Levy 2013-06-03, 05:28
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Stefan Krawczyk 2013-06-04, 01:28
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Philip Zeyliger 2013-06-04, 18:24
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Re: Python-Avro Codegen Proposal
Tal Levy 2013-06-04, 20:54
I will try and clean it up and set up a patch to submit via JIRA

here are the changes

https://github.com/talevy/avro/tree/python-codegen

a few caveats and thoughts about my current version:

1. I do not know how to best handle constructors, because some fields are
not allowed to be null... maybe a builder pattern would work here, but it's
kind of weird in python
2. I copy/pasted a lot of the code from SpecificCompiler to make the
PythonCompiler... some renaming and code re-use via inheritance would make
it read better.
3. I wanted to reuse the validate methods provided already in Avro to
verify the record, but it takes away from some of the class type
correctness for nested records and such.
4. I do not know what the best way of outputing multiple files is, I
currently use the same packaging as the java classes into their namespace
directories
5. I am not familiar with the avro-protocol format, so I only implemented
enums and records.

I updated the SpecificCompilerTool to have the following usage

```
"Usage: [-string] (schema|protocol) (python|java) input... outputdir"
````

So generating the python classes is as easy as java.
let me know what you think
On Tue, Jun 4, 2013 at 11:24 AM, Philip Zeyliger <[EMAIL PROTECTED]>wrote:

> Hi Tal,
>
> I would encourage you to file a JIRA and contribute your changes!
>
> I agree that the generated code approach is a great one for things like RPC
> usage, where the schema changes slowly and the extra checking is super
> handy.
>
> -- Philip
>
>
> On Mon, Jun 3, 2013 at 6:28 PM, Stefan Krawczyk <[EMAIL PROTECTED]>
> wrote:
>
> > Hi Tal,
> >
> > I'm interested in using Avro + Python. That would sound useful, any
> chance
> > I could have a play with what you've done?
> >
> > Cheers,
> >
> > Stefan
> >
> >
> > On Sun, Jun 2, 2013 at 10:28 PM, Tal Levy <[EMAIL PROTECTED]> wrote:
> >
> > > Hi,
> > >
> > > I recently started using Avro at my work and we found it difficult to
> > keep
> > > track of what python dict matched to what schema. Instead of having
> > > random dicts being populated and then attempted to be serialized to
> > avro, I
> > > thought
> > > it would be more readable and less error prone to codegen the python
> dict
> > > for developers. These classes are type checked field by field. Although
> > it
> > > does not
> > > have the advantage of compiled type checking like in the java codegen,
> it
> > > is a
> > > friendly wrapper around python dicts representing avro records to be
> > > serialized.
> > >
> > > let me know what you think about this, I am still tweaking how it
> > behaves.
> > > I understand it is a bit unpythonic to enforce types in this way, but
> the
> > > readability
> > > is worth it nonetheless.
> > >
> > > here is an example record:
> > > https://gist.github.com/talevy/5696236
> > >
> > > I extended the avro compiler/tools to provide both java and python
> > codegen
> > > functionality.
> > > so if this sounds like something others would use, maybe it makes sense
> > to
> > > include it
> > > into the main repo.
> > >
> > >
> > > Thanks,
> > > Tal
> > >
> >
>
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Philip Zeyliger 2013-06-05, 00:16
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Tal Levy 2013-06-05, 00:58