str与bytes

>>> a = u"hello"
>>> b = b"hello"
>>> c = "hello"

>>> type(a), type(a.encode("utf8")), type(a.decode("utf8"))
(<type 'unicode'>, <type 'str'>, <type 'unicode'>)
>>> type(b), type(b.encode("utf8")), type(b.decode("utf8"))
(<type 'str'>, <type 'str'>, <type 'unicode'>)
>>> type(c), type(c.encode("utf8")), type(c.decode("utf8"))
(<type 'str'>, <type 'str'>, <type 'unicode'>)

unicode.encode() => str
str.decode() => unicode

>>> a = "hello"
>>> b = b"hello"

>>> type(a), type(a.encode("utf8"))
(<class 'str'>, <class 'bytes'>)
>>> type(b), type(b.decode("utf8"))
(<class 'bytes'>, <class 'str'>)

str.encode() => bytes
bytes.decode() => str