Python2的编解码
python2中程序数据类型默认为ASCII，所以需要先将数据解码（decode）成为Unicode类型，然后再编码（encode）成为想要转换的数据类型（gbk，utf-8，gb18030，gb2312），然后再解码成为对应的数据类型显示在屏幕上；
Python3的编解码
python3中程序默认数据类型为Unicode，所以直接将数据编码（encode）成为想要转换的数据类型（gbk，utf-8，gb18030，gb2312），然后解码成为对应的数据类型显示在屏幕上。
base64
Base64编码是一种“防君子不防小人”的编码方式。广泛应用于MIME协议，作为电子邮件的传输编码，生成的编码可逆，后一两位可能有“=”，生成的编码都是ascii字符。
因此对于python2来说，编解码相对要容易一些。python3因为要从Unicode转换一下，相对麻烦一些。一切见下例：
- Python2
1 def b64encode(s, altchars=None):
2 """Encode a string using Base64.
3
4 s is the string to encode. Optional altchars must be a string of at least
5 length 2 (additional characters are ignored) which specifies an
6 alternative alphabet for the '+' and '/' characters. This allows an
7 application to e.g. generate url or filesystem safe Base64 strings.
8
9 The encoded string is returned.
10 """
11 # Strip off the trailing newline
12 encoded = binascii.b2a_base64(s)[:-1]
13 if altchars is not None:
14 return encoded.translate(string.maketrans(b'+/', altchars[:2]))
15 return encoded
1 def b64decode(s, altchars=None):
2 """Decode a Base64 encoded string.
3
4 s is the string to decode. Optional altchars must be a string of at least
5 length 2 (additional characters are ignored) which specifies the
6 alternative alphabet used instead of the '+' and '/' characters.
7
8 The decoded string is returned. A TypeError is raised if s is
9 incorrectly padded. Characters that are neither in the normal base-64
10 alphabet nor the alternative alphabet are discarded prior to the padding
11 check.
12 """
13 if altchars is not None:
14 s = s.translate(string.maketrans(altchars[:2], '+/'))
15 try:
16 return binascii.a2b_base64(s)
17 except binascii.Error, msg:
18 # Transform this exception for consistency
19 raise TypeError(msg)这里面的s是一个字符串类型的对象。
1 import base64
2
3 s = 'Hello, python'
4 b = base64.b64encode(s)
5 print 'b为：', b
6
7 c = base64.b64decode(b)
8 print 'c为：', c
9
10
11 # output
12 b为： SGVsbG8sIHB5dGhvbg==
13 c为： Hello, python- Python3
1 def b64encode(s, altchars=None):
2 """Encode the bytes-like object s using Base64 and return a bytes object.
3
4 Optional altchars should be a byte string of length 2 which specifies an
5 alternative alphabet for the '+' and '/' characters. This allows an
6 application to e.g. generate url or filesystem safe Base64 strings.
7 """
8 encoded = binascii.b2a_base64(s, newline=False)
9 if altchars is not None:
10 assert len(altchars) == 2, repr(altchars)
11 return encoded.translate(bytes.maketrans(b'+/', altchars))
12 return encoded
1 def b64decode(s, altchars=None, validate=False):
2 """Decode the Base64 encoded bytes-like object or ASCII string s.
3
4 Optional altchars must be a bytes-like object or ASCII string of length 2
5 which specifies the alternative alphabet used instead of the '+' and '/'
6 characters.
7
8 The result is returned as a bytes object. A binascii.Error is raised if
9 s is incorrectly padded.
10
11 If validate is False (the default), characters that are neither in the
12 normal base-64 alphabet nor the alternative alphabet are discarded prior
13 to the padding check. If validate is True, these non-alphabet characters
14 in the input result in a binascii.Error.
15 """
16 s = _bytes_from_decode_data(s)
17 if altchars is not None:
18 altchars = _bytes_from_decode_data(altchars)
19 assert len(altchars) == 2, repr(altchars)
20 s = s.translate(bytes.maketrans(altchars, b'+/'))
21 if validate and not re.match(b'^[A-Za-z0-9+/]*={0,2}$', s):
22 raise binascii.Error('Non-base64 digit found')
23 return binascii.a2b_base64(s)这里面的s是一个bytes对象，则字符串首先要经过编码encode()。经过b64encode/b64decode之后的返回结果也是bytes对象，所以我们要转换为Unicode对象就要再使用decode()方法去解码。
1 import base64
2
3 s = 'Hello, Python!'
4 b = base64.b64encode(s.encode('utf-8')).decode('utf-8')
5 print(b)
6
7 c = base64.b64decode(b.encode('utf-8')).decode('utf-8')
8 print(c)
9
10 # output
11 SGVsbG8sIFB5dGhvbiE=
12 Hello, Python!来源：oschina
链接：https://my.oschina.net/u/4396169/blog/3596303