How to pickle and unpickle to portable string in Python 3

Question

I need to pickle a Python3 object to a string which I want to unpickle from an environmental variable in a Travis CI build. The problem is that I can\'t seem to find a way t

Answer 1

I think the simplest answer, especially if you don't care about Windows, is to just store the bytes in the environment, as suggested in my other answer.

But if you want something clean and debuggable, you might be happier using something designed as a text-based format.

pickle does have a "plain text" protocol 0, as explained in kindall's answer. It's certainly more readable than protocol 3 or 4, but it's still not something I'd actually want to read.

JSON is much nicer, but it can't handle datetime out of the box. You can come up with your own encoding (the stdlib's json module is extensible) for the handful of types you need to encode, or use something like jsonpickle. It's generally safer, more efficient, and more readable to come up with custom encodings for each type you care about than a general "pack arbitrary types in a turing-complete protocol" scheme like pickle or jsonpickle, but of course it's also more work, especially if you have a lot of extra types.

JSON Schema lets you define languages in JSON, similar to what you'd do in XML. It comes with a built-in date-time String format, and the jsonschema library for Python knows how to use it.

YAML has a standard extension repository that includes many types JSON doesn't, including a timestamp. Most of the zillion 'yaml' modules for Python already know how to encode datetime objects to and from this type. If you need additional types beyond what YAML includes, it was designed to be extensible declaratively. And there are libraries that do the equivalent of jsonpickle, defining new types on the fly, if you really need that.

And finally, you can always write an XML language.