UnicodeDecodeError while using json.dumps()

Question

I have strings as follows in my python list (taken from command prompt):

>>> o['records'][5790]
(5790, 'Vlv-Gate-Assy-Mdl-\xe1M1-2-\xe19/16-10K-BB Credit Memo            ', 60,
 True, '40141613')
>>>

I have tried suggestions as mentioned here: Changing default encoding of Python?

Further changed the default encoding to utf-16 too. But still json.dumps() threw and exception as follows:

>>> write(o)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "okapi_create_master.py", line 49, in write
    o = json.dumps(output)
  File "C:\Python27\lib\json\__init__.py", line 231, in dumps
    return _default_encoder.encode(obj)
  File "C:\Python27\lib\json\encoder.py", line 201, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "C:\Python27\lib\json\encoder.py", line 264, in iterencode
    return _iterencode(o, 0)
UnicodeDecodeError: 'utf8' codec can't decode byte 0xe1 in position 25: invalid
continuation byte

Can't figure what kind of transformation is required for such strings so that json.dumps() works.

Solution 1

\xe1 is not decodable using utf-8, utf-16 encoding.

>>> '\xe1'.decode('utf-8')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\encodings\utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeDecodeError: 'utf8' codec can't decode byte 0xe1 in position 0: unexpected end of data
>>> '\xe1'.decode('utf-16')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\encodings\utf_16.py", line 16, in decode
    return codecs.utf_16_decode(input, errors, True)
UnicodeDecodeError: 'utf16' codec can't decode byte 0xe1 in position 0: truncated data

Try latin-1 encoding:

>>> record = (5790, 'Vlv-Gate-Assy-Mdl-\xe1M1-2-\xe19/16-10K-BB Credit Memo            ',
...           60, True, '40141613')
>>> json.dumps(record, encoding='latin1')
'[5790, "Vlv-Gate-Assy-Mdl-\\u00e1M1-2-\\u00e19/16-10K-BB Credit Memo            ", 60, true, "40141613"]'

Or, specify ensure_ascii=False, json.dumps to make json.dumps not try to decode the string.

>>> json.dumps(record, ensure_ascii=False)
'[5790, "Vlv-Gate-Assy-Mdl-\xe1M1-2-\xe19/16-10K-BB Credit Memo            ", 60, true, "40141613"]'

Solution 2

I had a similar problem, and came up with the following approach to either guarantee unicodes or byte strings, from either input. In short, include and use the following lambdas:

# guarantee unicode string
_u = lambda t: t.decode('UTF-8', 'replace') if isinstance(t, str) else t
_uu = lambda *tt: tuple(_u(t) for t in tt) 
# guarantee byte string in UTF8 encoding
_u8 = lambda t: t.encode('UTF-8', 'replace') if isinstance(t, unicode) else t
_uu8 = lambda *tt: tuple(_u8(t) for t in tt)

Applied to your question:

import json
o = (5790, u"Vlv-Gate-Assy-Mdl-\xe1M1-2-\xe19/16-10K-BB Credit Memo            ", 60,
 True, '40141613')
as_json = json.dumps(_uu8(*o))
as_obj = json.loads(as_json)
print "object\n ", o
print "json (type %s)\n %s " % (type(as_json), as_json)
print "object again\n ", as_obj

=>

object
  (5790, u'Vlv-Gate-Assy-Mdl-\xe1M1-2-\xe19/16-10K-BB Credit Memo            ', 60, True, '40141613')
json (type <type 'str'>)
  [5790, "Vlv-Gate-Assy-Mdl-\u00e1M1-2-\u00e19/16-10K-BB Credit Memo            ", 60, true, "40141613"]
object again
  [5790, u'Vlv-Gate-Assy-Mdl-\xe1M1-2-\xe19/16-10K-BB Credit Memo            ', 60, True, u'40141613']

Here's some more reasoning about this.