New submission from Tom Christie:
This is one of those behavioural issues that is a borderline bug.
The seperators argument to `json.dumps()` behaves differently across python 2
and 3.
* In python 2 it should be provided as a bytestring, and can cause a
UnicodeDecodeError otherwise.
* In python 3 it should be provided as unicode,and can cause a TypeError
otherwise.
Examples:
Python 2.7.2
>>> print json.dumps({'snowman': '☃'}, separators=(':', ','),
ensure_ascii=False)
{"snowman","☃"}
>>> print json.dumps({'snowman': '☃'}, separators=(u':', u','),
ensure_ascii=False)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 1:
ordinal not in range(128)
And:
Python 3.4.0
>>> print(json.dumps({'snowman': '☃'}, separators=(':', ','),
ensure_ascii=False))
{"snowman","☃"}
>>> print(json.dumps({'snowman': '☃'}, separators=(b':', b','),
ensure_ascii=False))
<...>
TypeError: sequence item 2: expected str instance, bytes found
Technically this isn't out of line with the documentation - in both cases it
uses `separators=(':', ',')` which is indeed the correct type in both v2 and
v3. However it's unexpected behaviour that it changes types between versions,
without being called out.
Working on a codebase with `from __future__ import unicode_literals` this is
particularly unexpected because we get a `UnicodeDecodeError` when running code
that otherwise looks correct.
It's also slightly awkward to fix because it's a bit of a weird branch
condition.
The fix would probably be to forcibly coerce it to the correct type regardless
of if it is supplied as unicode or a bytestring, or at least to do so for
python 2.7.
Possibly related to http://bugs.python.org/issue22701 but wasn't able to
understand if that ticket was in fact a different user error.
----------
messages: 230274
nosy: Tom.Christie
priority: normal
severity: normal
status: open
title: `separators` argument to json.dumps() behaves unexpectedly across 2.x vs
3.x
type: behavior
versions: Python 2.7, Python 3.4
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue22767>
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