file encoding in python3

encoding.txt

λ python3
Python 3.6.1 (default, Apr  4 2017, 09:36:47) 
[GCC 4.2.1 Compatible Apple LLVM 7.0.2 (clang-700.1.81)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> b'abc\n'
b'abc\n'
>>> a = _
>>> list(a)
[97, 98, 99, 10]
>>> a.decode(encoding='utf_8')
'abc\n'
>>> a.decode(encoding='utf_16')
'扡\u0a63'
>>> a.decode(encoding='utf_32')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeDecodeError: 'utf-32-le' codec can't decode bytes in position 0-3: code point not in range(0x110000)
>>>