PyMOTW: base64 =============== .. currentmodule:: base64 * 模块： base64 * 目的： 编码二进制数据转化为ASCII码 * python版本： 1.4+ base64模块提供一些函数l来把二进制数据转换为ASCII集, 通常在明文协议的传输中使用. 描述 ---- base64、base32、base16可以分别编码转化8位字节为6位、5位、4位, 允许非ASCII字节以编码为ASCII码的协议中传输, 例如SMTP, "base"值对应是在每一个编码中字母表的长度. 有一些原始编码的url类型会使用略有不同的结果. Base64 编码 --------------- 简单的文本编码示例如下: .. code-block:: python import base64 initial_data = open(__file__, 'rt').read() encoded_data = base64.b64encode(initial_data) num_initial = len(initial_data) padding = { 0:0, 1:2, 2:1 }[num_initial % 3] print '%d bytes before encoding' % num_initial print 'Expect %d padding bytes' % padding print '%d bytes after encoding' % len(encoded_data) print print encoded_data 输出显示原来529字节的文本在编码之后被扩展到了708个字节, 从编码过程来看, 每一个24位序列(3个字节)作为输入, 输出时候则增加了4个字节, 最后2个字符"==", 则是简单的追加, 因为原始字符串的位数不能被24整除. 在标准输出中时没有很多回车府, 但是为了在文档中有好的可读性, 在如下显示中稍作了变化. :: $ python base64_b64encode.py 529 bytes before encoding Expect 2 padding bytes 708 bytes after encoding IyEvdXNyL2Jpbi9lbnYgcHl0aG9uCiMgZW5jb2Rpbmc 6IHV0Zi04CiMKIyBDb3B5cmlnaHQgKGMpIDIwMDggRG 91ZyBIZWxsbWFubiBBbGwgcmlnaHRzIHJlc2VydmVkL gojCiIiIgoiIiIKCl9fdmVyc2lvbl9fID0gIiRJZDog cHltb3R3LnB5IDEyMzkgMjAwOC0wMS0xNiAxMDo1NTo xOVogZGhlbGxtYW5uICQiCgppbXBvcnQgYmFzZTY0Cg ppbml0aWFsX2RhdGEgPSBvcGVuKF9fZmlsZV9fLCAnc nQnKS5yZWFkKCkKCmVuY29kZWRfZGF0YSA9IGJhc2U2 NC5iNjRlbmNvZGUoaW5pdGlhbF9kYXRhKQoKbnVtX2l uaXRpYWwgPSBsZW4oaW5pdGlhbF9kYXRhKQpwYWRkaW 5nID0geyAwOjAsIDE6MiwgMjoxIH1bbnVtX2luaXRpY WwgJSAzXQoKcHJpbnQgJyVkIGJ5dGVzIGJlZm9yZSBl bmNvZGluZycgJSBudW1faW5pdGlhbApwcmludCAnRXh wZWN0ICVkIHBhZGRpbmcgYnl0ZXMnICUgcGFkZGluZw pwcmludCAnJWQgYnl0ZXMgYWZ0ZXIgZW5jb2RpbmcnI CUgbGVuKGVuY29kZWRfZGF0YSkKcHJpbnQKcHJpbnQg ZW5jb2RlZF9kYXRhCg== Base64 解码 -------------- 编码的字符串可以转换为原来的格式, 利用反向查询, 把4个字节转换为3个字节. b64decode()函数可以帮助你. .. code-block:: python import base64 original_string = 'This is the data, in the clear.' print 'Original:', original_string encoded_string = base64.b64encode(original_string) print 'Encoded :', encoded_string decoded_string = base64.b64decode(encoded_string) print 'Decoded :', decoded_string :: $ python base64_b64decode.py Original: This is the data, in the clear. Encoded : VGhpcyBpcyB0aGUgZGF0YSwgaW4gdGhlIGNsZWFyLg== Decoded : This is the data, in the clear. URL-Safe变化 -------------- 默认的base64字母表可能会使用+和/, 而这些字符可能出现在url中, 因此必须为这些字符指定可选择的编码情况, +由a-来代替, (_)来代替/, 其他字母表还是相同. .. code-block:: python import base64 for original in [ '\xfb\xef', '\xff\xff' ]: print 'Original :', repr(original) print 'Standard encoding:', base64.standard_b64encode(original) print 'URL-safe encoding:', base64.urlsafe_b64encode(original) print :: $ python base64_urlsafe.py Original : '\xfb\xef' Standard encoding: ++8= URL-safe encoding: --8= Original : '\xff\xff' Standard encoding: //8= URL-safe encoding: __8= 其他编码 ------------ 除了base 64以外, 还有base 32和base 16(16进制)提供函数用于编码数据. .. code-block:: python import base64 original_string = 'This is the data, in the clear.' print 'Original:', original_string encoded_string = base64.b32encode(original_string) print 'Encoded :', encoded_string decoded_string = base64.b32decode(encoded_string) print 'Decoded :', decoded_string :: $ python base64_base32.py Original: This is the data, in the clear. Encoded : KRUGS4ZANFZSA5DIMUQGIYLUMEWCA2LOEB2GQZJAMNWGKYLSFY====== Decoded : This is the data, in the clear. base 16中的函数是以16进制方式工作. .. code-block:: python import base64 original_string = 'This is the data, in the clear.' print 'Original:', original_string encoded_string = base64.b16encode(original_string) print 'Encoded :', encoded_string decoded_string = base64.b16decode(encoded_string) print 'Decoded :', decoded_string :: $ python base64_base16.py Original: This is the data, in the clear. Encoded : 546869732069732074686520646174612C20696E2074686520636C6561722E Decoded : This is the data, in the clear. 参考 ----- * `RFC 3548 - The Base16, Base32, and Base64 Data Encodings `_