Question

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

Answer 1

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.)