pymarshal

PyMarshal

pymarshal replicates the feature of (un)marshalling structs in Golang. Rather than replicating the exact feature as it exists in Go, pymarshal aims for elegant, Pythonic simplicity, and to fix the flaws in Go's implementation such as:

• extra keys being silently ignored
• lack of mandatory fields
• lack of default values See control variables for the many options that can be configured per-class.

PyMarshal v2.0+

Support for the following has been removed:

• YAML docstring API docs format
• Python2

If you need any of these, use 1.6.2

Currently supported serialization formats

• JSON
• BSON
• YAML
• CSV

As YAML is compatible with JSON, use PyYAML to load or dump data with the pymarshal.json module, there is no explicit YAML module.

Installation

It is recommended that you install from PyPI using pip install pymarshal

Overview

The only modification required to your class code is to use the type_assert functions to assign __init__ arguments to class fields of the same name. pymarshal provides the type_assert functions to both enforce the type, and to unmarshal nested objects.

Example:

class MyModel:
    def __init__(
        self,
        a,
        b=5,
    ):
        self.a = type_assert(a, str)
        self.b = type_assert(b, int)

>>> from pymarshal.json import *
>>> x = marshal_json(MyModel("test", 6))
>>> x
{"a": "test", "b": 6}
>>> y = unmarshal_json(x, MyModel)
>>> y.a
"test"

NOTE: Your classes must not implement __call__ (which is an antipattern anyway). Whatever you would've implemented with __call__ should just be a normal, named method.

Your __init__ methods should only use simple assignment through the type_assert functions. If you have a use-case for a constructor that does more than simple assignment, use a separate 'factory' static method.

There is also:

• type_assert_iter for iterables
• type_assert_dict for anything that implements .items() -> k, v

Rather than using the Golang "tag" syntax, simply create a _marshal_key_swap and _unmarshal_key_swap dict in your class, and any re-named keys will be swapped before being passed to the class constructor or before being marshalled to JSON. The full list of control variables are documented HERE.

Examples

See the documentation folder