Forcing Python json module to work with ASCII

Question

I'm using json.dump() and json.load() to save/read a dictionary of strings to/from disk. The issue is that I can't have any of the strings in unicode. They seem to be in unicode no matter how I set the parameters to dump/load (including ensure_ascii and encoding).

Answer 1

If you are just dealing with simple JSON objects, you can use the following:

def ascii_encode_dict(data):
    ascii_encode = lambda x: x.encode('ascii')
    return dict(map(ascii_encode, pair) for pair in data.items())

json.loads(json_data, object_hook=ascii_encode_dict)

Here is an example of how it works:

>>> json_data = '{"foo": "bar", "bar": "baz"}'
>>> json.loads(json_data)                                # old call gives unicode
{u'foo': u'bar', u'bar': u'baz'}
>>> json.loads(json_data, object_hook=ascii_encode_dict) # new call gives str
{'foo': 'bar', 'bar': 'baz'}

This answer works for a more complex JSON structure, and gives some nice explanation on the object_hook parameter. There is also another answer there that recursively takes the result of a json.loads() call and converts all of the Unicode strings to byte strings.

Answer 2

And if the json object is a mix of datatypes, not only unicode strings, you can use this expression:

def ascii_encode_dict(data):
    ascii_encode = lambda x: x.encode('ascii') if isinstance(x, unicode) else x 
    return dict(map(ascii_encode, pair) for pair in data.items())