AttributeError:’bytes’ object has no attribute ‘encode’

If you don’t know if a stringlike object is a Python 2 string (bytes) or Python 3 string (unicode). You could have a generic converter.

Python3 shell:

>>> def to_bytes(s):
...     if type(s) is bytes:
...         return s
...     elif type(s) is str or (sys.version_info[0] < 3 and type(s) is unicode):
...         return codecs.encode(s, 'utf-8')
...     else:
...         raise TypeError("Expected bytes or string, but got %s." % type(s))
...         
>>> to_bytes("hello")
b'hello'
>>> to_bytes("hello".encode('utf-8'))
b'hello'

On Python 2 both these expressions evaluate to True: type("hello") == bytes and type("hello") == str. And type(u"hello") == str evaluates to False, while type(u"hello") == unicode is True.

On Python 3 type("hello") == bytes is False, and type("hello") == str is True. And type("hello") == unicode raises a NameError exception since unicode isn’t defined on 3.

Python 2 shell:

>>> to_bytes(u"hello")
'hello'
>>> to_bytes("hello")
'hello'