Hello Python pickle

思路

• pickle 是什麼

• Hello pickle!

• pickle 能解析什麼？

• 自定義的類怎麼使用 pickle

pickle

pickle 是 Python 裏的序列化工具。

pickle can save and restore class instances transparently, however the class definition must be importable and live in the same module as when the object was stored.

Hello pickle

>>> import pickle
>>> s = 'Hello pickle~'
>>> sp = pickle.dumps(s)
>>> "S'Hello pickle'\np0\n."
>>> sp
>>> pickle.loads(sp)

pickle 能解析什麼

• string ?

• simple dict ?

• datetime ?

>>> pickle.loads(pickle.dumps({'a': 'aaa', 'n': 123}))
{'a': 'aaa', 'n': 123}

>>> pickle.dumps(datetime.datetime.now())
"cdatetime\ndatetime\np0\n(S'\\x07\\xe0\\x05\\x1f\\x0e:\\x15\\x03\\x17\\xde'\np1\ntp2\nRp3\n."

>>> pickle.loads("cdatetime\ndatetime\np0\n(S'\\x07\\xe0\\x05\\x1f\\x0e:\\x15\\x03\\x17\\xde'\np1\ntp2\nRp3\n.")
datetime.datetime(2016, 5, 31, 14, 57, 51, 537279)

11.1.4. What can be pickled and unpickled?

寫一個 picklable 的類

發現以下的類是能夠直接 pickle 的，且 unpickle 的地方只要引用過了 User Class 就能夠成功 unpickle。

class User(object):
    def __init__(self, id, name):
        self.id = id
        self.name = name

>>> u1 = User(1, 'a')
>>> pickle.dumps(u1)
"ccopy_reg\n_reconstructor\np0\n(c__main__\nUser\np1\nc__builtin__\nobject\np2\nNtp3\nRp4\n(dp5\nS'id'\np6\nI1\nsS'name'\np7\nS'a'\np8\nsb."