>>> from marshal import dump, load, dumps, loads

>>> s = dumps(range(10))
>>> s
'[\n\x00\x00\x00i\x00\...\x00\x00'

>>> loads(s)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

保存序列化結(jié)果到文件。

>>> with file("test.dat", "w") as f:
...     dump(range(10), f)

>>> with file("test.dat", "r") as f:
...     print load(f)

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

pickle

應(yīng)該用 cPickle 代替 pickle，按官方文檔的說法有千倍的提升，且可相互替換。支持用戶自定義類型，支持三種協(xié)議版本：

0: 使用可顯示的 ASCII 字符編碼，便于閱讀和手工編輯。(默認)
1: 兼容早期 Python 版本的二進制格式。
2: 最有效的二進制編碼格式。

>>> import pickle, cPickle

>>> s = "Hello, World"
>>> d = cPickle.dumps(s, 2)
>>> d
'\x80\x02U\rHello, Worldq\x01.'

>>> cPickle.loads(d)
'Hello, World'

>>> pickle.loads(d)   # 和 pickle 格式完全相同。
'Hello, World'

同樣有讀寫文件的 dump、load 函數(shù)?？纯粗С值臄?shù)據(jù)類型：

None, True, False
int, long, float, complex
str, unicode
tuple, list, set, and dict (元素必須是支持類型)
function (模塊級別的函數(shù))
classe (模塊級別的自定義類，非嵌套)
instance (有 dict 屬性，或者實現(xiàn) pickle protocol 協(xié)議)

看看對自定義類型的測試。

>>> class Data(object):
...     def __init__(self, x, y):
...         print "__init__"
...         self._x = x
...         self._y = y

>>> d = Data(100, 200)
__init__

>>> s = cPickle.dumps(d, 2)

>>> d2 = cPickle.loads(s)  # 反序列化并沒有調(diào)用 __init__
>>> d2.__dict__
{'_x': 100, '_y': 200}

利用 pickle protocol 可以控制序列化的細節(jié)。比如下面例子中，我們不像保留 _y 字段。

>>> class Data(object):
...     def __init__(self, x, y):
...         self._x = x
...         self._y = y
...
...     def __getstate__(self):
...         d = self.__dict__.copy()
...         del d["_y"]
...     return d
...
...     def __setstate__(self, state):
...         self.__dict__.update(state)

>>> d = Data(10, 20)

>>> s = cPickle.dumps(d, 2)

>>> d2 = cPickle.loads(s)
>>> d2.__dict__
{'_x': 10}

shevle

將對象 pickle 序列化，然后保存到 anydbm 格式文件。anydbm 是個 KV 結(jié)構(gòu)的數(shù)據(jù)庫，可以保存多個序列化的對象。當然也可以選擇使用 dbm、gdbm、bdb。

flag: r 讀, w 寫, c 讀寫, n 新建、讀寫。
protocol: pickle 版本。
writeback: 允許將變更的對象同步到數(shù)據(jù)庫。(還是顯式修改保存比較好)

>>> import shelve
>>> from contextlib import closing

>>> with closing(shelve.open("test", protocol = 2)) as f:
... f["a"] = dict(name = "Tom", age = 34, sex = "male")
... f["b"] = (1, ["a", 3], "abcdefg")

>>> !xxd -g 1 -l 100 test.db
0000000: 00 06 15 61 00 00 00 02 00 00 04 d2 00 00 10 00 ...a............
0000010: 00 00 00 0c 00 00 01 00 00 00 01 00 00 00 00 08 ................
0000050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0000060: 00 00 00 00 ....

>>> with closing(shelve.open("test", protocol = 2)) as f:
...     print f["a"]
...     print f["b"]
...     print ["c"]

{'age': 34, 'name': 'Tom', 'sex': 'male'}
(1, ['a', 3], 'abcdefg')
['c']