There is no way to json encode object to str.

[kaltovichartyom]

BPO	42791
Nosy	@rhettinger, @ezio-melotti, @iritkatriel

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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assignee = None
closed_at = None
created_at = <Date 2020-12-30.20:22:51.914>
labels = ['library']
title = 'There is no way to json encode object to str.'
updated_at = <Date 2021-08-31.20:34:24.741>
user = 'https://bugs.python.org/kaltovichartyom'

bugs.python.org fields:

activity = <Date 2021-08-31.20:34:24.741>
actor = 'iritkatriel'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-12-30.20:22:51.914>
creator = 'kaltovichartyom'
dependencies = []
files = []
hgrepos = []
issue_num = 42791
keywords = []
message_count = 2.0
messages = ['384085', '400776']
nosy_count = 4.0
nosy_names = ['rhettinger', 'ezio.melotti', 'iritkatriel', 'kaltovichartyom']
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priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue42791'
versions = []

[kaltovichartyom]

Hello.

At first I want to say thank you for all your efforts in python development. I really appreciate it. :)

I am trying to convert custom object to json.

But, I've found a problem. JSONEncoder has default method for converting custom objects to some primitives and encode for converting structures.

But what if I want to return completed json string? I can't do it in default, because JSONEncoder will think it is string and encode it accordingly later in iterencode method.

Then I tried redefine encode, but it is called with the dict(array_name=default(o)) so I should convert the dict as a whole and basically reimplement all conversions (for int, float, and lists of course).

Did I missed something or there is no way to do it?

I suggest to introduce another method, e.g. encode_obj and call it there:

https://github.com/python/cpython/blob/master/Lib/json/encoder.py#L438

 o = _default(o)
 yield from _iterencode(o, _current_indent_level)

->

 o = _encode_obj(_default(o))
 yield from _iterencode(o, _current_indent_level)

If you are agree I would be happy to implement it.

Best Regards,
Artsiom.

[iritkatriel]

See also bpo-35111.