New submission from July Tikhonov:
According to documentation of json.dump(), concerning its 'default' option:
default(obj) is a function that should return a serializable version of obj or
raise TypeError. The default simply raises TypeError.
But this function is actually never applied to serialized dictionary keys:
>>> def default(obj):
... if isinstance(obj, bytes):
... return obj.decode('ascii')
... raise ValueError
...
>>> json.dumps(b'asdf')
Traceback (most recent call last):
...
TypeError: b'asdf' is not JSON serializable
>>> json.dumps(b'asdf', default=default)
'"asdf"'
>>> json.dumps({b'asdf' : 1}, default=default)
Traceback (most recent call last):
...
TypeError: keys must be a string
>>> json.dumps({1 : b'asdf'}, default=default)
'{"1": "asdf"}'
(bytes are used purely for the purpose of example)
Such behavior should be either documented or corrected.
Patch correcting python implementation of json attached.
----------
assignee: docs@python
components: Documentation, Library (Lib)
files: json-default-dict-keys.diff
keywords: patch
messages: 195957
nosy: docs@python, july
priority: normal
severity: normal
status: open
title: json.dump() ignores its 'default' option when serializing dictionary keys
type: enhancement
versions: Python 3.4
Added file: http://bugs.python.org/file31436/json-default-dict-keys.diff
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue18820>
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