bytearray([source [, encoding [, errors]]])
中文說明：
bytearray([source [, encoding [, errors]]])返回一個byte陣列。Bytearray型別是一個可變的序列，並且序列中的元素的取值範圍為 [0 ,255]。
引數source:
如果source為整數，則返回一個長度為source的初始化陣列；
如果source為字串，則按照指定的encoding將字串轉換為位元組序列；
如果source為可迭代型別，則元素必須為[0 ,255]中的整數；
如果source為與buffer介面一致的物件，則此物件也可以被用於初始化bytearray.。
版本：在python2.6後新引入，在python3中同樣可以使用！
英文說明:
Return a new array of bytes. The bytearray type is a mutable sequence of integers in the range 0 <= x < 256. It has most of the usual methods of mutable sequences, described in Mutable Sequence Types, as well as most methods that the str type has, see String Methods.
The optional source parameter can be used to initialize the array in a few different ways:
If it is a string, you must also give the encoding (and optionally, errors) parameters; bytearray() then converts the string to bytes using str.encode().
If it is an integer, the array will have that size and will be initialized with null bytes.
If it is an object conforming to the buffer interface, a read-only buffer of the object will be used to initialize the bytes array.
If it is an iterable, it must be an iterable of integers in the range 0 <= x < 256, which are used as the initial contents of the array.
Without an argument, an array of size 0 is created.
New in version 2.6.
例項演示：
>>> a = bytearray(3)
>>> a
bytearray(b'\x00\x00\x00')
>>> a[0]
>>> a[1]
>>> a[2]
>>> b = bytearray("abc")
>>> b
bytearray(b'abc')
>>> b[0]
>>> b[1]
>>> b[2]
>>> c = bytearray([1, 2, 3])
>>> c
bytearray(b'\x01\x02\x03')
>>> c[0]
>>> c[1]
>>> c[2]
>>> d = bytearray(buffer("abc"))
>>> d
bytearray(b'abc')
>>> d[0]
>>> d[1]
>>> d[2]