Hey I'm new here, so please let me know what incorrect things I am doing!

I _think_ `json.dumps(o, ensure_ascii=False)` is doing the wrong thing when `o` has both unicode and str keys/values. For instance:

```
import json
o = {u"greeting": "hi", "currency": "€"}
json.dumps(o, ensure_ascii=False, encoding="utf8")
json.dumps(o, ensure_ascii=False)
```

The first `dumps` will work while the second will fail. the reason is:

https://github.com/python/cpython/blob/2.7/Lib/json/encoder.py#L198

This will decode any str if the encoding is not 'utf-8'. In the mixed case (unicode and str) this will blow. I workaround is to use any of the aliases for 'utf-8' like 'utf8' or 'u8'.

I would be crazy happy to provide a PR if this is really an issue.
Let me know if extra clarification is needed.
Nicolás

Treating 'utf-8' and its aliases differently (when they specifically mean the Python's, rather than something else's, encoding) is definitely as issue.

You shouldn't hardcode a list of aliases though; rather use existing facilities to resolve them. From quick googling, e.g. `codecs.lookup(<encoding>).name` can get the canonical name.


Make sure to follow https://devguide.python.org/pullrequest when doing the PR; a test case will likely be needed, too.

In simplejson:

>>> simplejson.dumps({u"greeting": "hi", "currency": "€"}, ensure_ascii=False, encoding="utf8")
u'{"currency": "\u20ac", "greeting": "hi"}'
>>> simplejson.dumps({u"greeting": "hi", "currency": "€"}, ensure_ascii=False)
u'{"currency": "\u20ac", "greeting": "hi"}'

I think it makes sense to fix the case for "utf-8".

Hi Sehriy,

I am ok with that change. I think it makes much more sense, but I also think it will break people's codes. At least with the simplest fix in which:

>>> json.dumps({"g"}, ensure_ascii=False)
u'"g"'

Which is again compatible with simplejson.
Although the documentation is not clear in this point there might be code out there relaying on this behaviour.
Is that acceptable?

You could decode only non-ascii strings.

But I'm not sure that it is worth to change something in 2.7. This could be treated aa a new feature. Left this on to Benjamin, the release manager of 2.7.