pythonunicodedecode

UnicodeDecodeError, invalid continuation byte


Why is the below item failing? Why does it succeed with "latin-1" codec?

o = "a test of \xe9 char" #I want this to remain a string as this is what I am receiving
v = o.decode("utf-8")

Which results in:

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 0xe9 in position 10: invalid continuation byte

Solution

  • In binary, 0xE9 looks like 1110 1001. If you read about UTF-8 on Wikipedia, you’ll see that such a byte must be followed by two of the form 10xx xxxx. So, for example:

    >>> b'\xe9\x80\x80'.decode('utf-8')
    u'\u9000'
    

    But that’s just the mechanical cause of the exception. In this case, you have a string that is almost certainly encoded in latin 1. You can see how UTF-8 and latin 1 look different:

    >>> u'\xe9'.encode('utf-8')
    b'\xc3\xa9'
    >>> u'\xe9'.encode('latin-1')
    b'\xe9'
    

    (Note, I'm using a mix of Python 2 and 3 representation here. The input is valid in any version of Python, but your Python interpreter is unlikely to actually show both unicode and byte strings in this way.)