json library fails to serialize objects such as datetime

[DannKe]

BPO	21543
Nosy	@4kir4

^{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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GitHub fields:

assignee = None
closed_at = <Date 2014-05-20.17:36:36.488>
created_at = <Date 2014-05-20.16:51:57.228>
labels = ['extension-modules', 'invalid', 'type-bug', 'library']
title = 'json library fails to serialize objects such as datetime'
updated_at = <Date 2014-05-20.17:36:36.487>
user = 'https://bugs.python.org/DannKe'

bugs.python.org fields:

activity = <Date 2014-05-20.17:36:36.487>
actor = 'r.david.murray'
assignee = 'none'
closed = True
closed_date = <Date 2014-05-20.17:36:36.488>
closer = 'r.david.murray'
components = ['Extension Modules', 'Library (Lib)']
creation = <Date 2014-05-20.16:51:57.228>
creator = 'Dann.Ke'
dependencies = []
files = []
hgrepos = []
issue_num = 21543
keywords = []
message_count = 3.0
messages = ['218849', '218852', '218853']
nosy_count = 2.0
nosy_names = ['akira', 'Dann.Ke']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue21543'
versions = ['Python 3.4']

[DannKe]

I'm using the json library to serialize objects out for web use.

Whenever I serialize a datetime or other included python library object (uuid as another example), it fails with

TypeError: datetime.datetime(2014, 5, 20, 9, 37, 56, 133627) is not JSON serializable

While this behaviour is well and good, what I am suggesting is that I would like a way for this library to attempt to serialize an object when it encounters an exception.

For instance, if it attempts to serialize a datetime and fails, I would like the option of submitting a method as a parameter to the json.dumps() method that the object is put into in an attempt to serialize it.

As a code example:

    import datetime, json
    json.dumps(dict(mydate=datetime.datetime.now()),
        serialize=str)

That way, when it encounters a TypeError, it will set mydate to a string and will be serialized out.

Right now, I have to use str() on a few different fields because they are not standard types (str, int, bool, float, None, etc)

This isn't a priority and I'm open to criticisms. Would you accept a patch for this if you are too busy to work on this feature?

Thank you for your time.
Dann

[4kir4]

json module already allows you to customize the serialization: see *default* parameter for json.dumps [1]

[1] https://docs.python.org/3/library/json.html#json.dump

[DannKe]

I was reading the older 2.7 docs and it didn't click that default() was
what I wanted. Thank you for clarifying.

On Tue, May 20, 2014 at 10:09 AM, akira <report@bugs.python.org> wrote:

akira added the comment:

json module already allows you to customize the serialization: see
*default* parameter for json.dumps [1]

[1] https://docs.python.org/3/library/json.html#json.dump

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nosy: +akira

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