[issue34858] MappingProxy objects should JSON serialize just like a dictionary
Raymond Hettinger
report at bugs.python.org
Sun Sep 30 23:26:23 EDT 2018
Raymond Hettinger <raymond.hettinger at gmail.com> added the comment:
IIRC, there was an early decision to handle only exact types and their subclasses (plus tuples). For example, os.environ and instances of collections.ChainMap are not JSON serializable.
I believe the reason was that it made encoding faster, more predictable, and more likely to match round-trip expectations. For those wanting more generality, there are at least two options. The simplest option is to coerce the input to supported type. A more complete solution is to write a subclass of JSONEncoder to pass into json.dump() as the *cls* argument (there are examples of how to do this in the docs).
For the specific case of mappingproxy, there is another issue. Multiple components of a class dict are not all JSON serializable, so you have the same problem yet again with getset_descriptor objects, member objects, and various slot wrappers.
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assignee: -> bob.ippolito
nosy: +bob.ippolito, rhettinger
versions: -Python 3.4, Python 3.5, Python 3.6, Python 3.7
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