看起来你遇到了一点麻烦!;-) 希望在此之后,你永远不会再使用pickle。它只是不是一个很好的数据存储格式。
无论如何,对于这个答案,我假设你的Document
类看起来有点像这样。如果不是,请在评论中提供您实际的Document
类:
class Document(object):
def __init__(self, title, date, text):
self.title = title
self.date = date
self.text = text
无论如何,我用这个类创建了一些简单的测试数据:
d = [Document(title='foo', text='foo is good', date='1/1/1'), Document(title='bar', text='bar is better', date='2/2/2'), Document(title='baz', text='no one likes baz :(', date='3/3/3')]
使用格式为2
(对于Python 2.x,使用pickle.HIGHEST_PROTOCOL
)进行了序列化处理。
>>> s = pickle.dumps(d, 2)
>>> s
'\x80\x02]q\x00(c__main__\nDocument\nq\x01)\x81q\x02}q\x03(U\x04dateq\x04U\x051/1/1q\x05U\x04textq\x06U\x0bfoo is goodq\x07U\x05titleq\x08U\x03fooq\tubh\x01)\x81q\n}q\x0b(h\x04U\x052/2/2q\x0ch\x06U\rbar is betterq\rh\x08U\x03barq\x0eubh\x01)\x81q\x0f}q\x10(h\x04U\x053/3/3q\x11h\x06U\x13no one likes baz :(q\x12h\x08U\x03bazq\x13ube.'
接着使用pickletools
对其进行解构:
>>> pickletools.dis(s)
0: \x80 PROTO 2
2: ] EMPTY_LIST
3: q BINPUT 0
5: ( MARK
6: c GLOBAL '__main__ Document'
25: q BINPUT 1
27: ) EMPTY_TUPLE
28: \x81 NEWOBJ
29: q BINPUT 2
31: } EMPTY_DICT
32: q BINPUT 3
34: ( MARK
35: U SHORT_BINSTRING 'date'
41: q BINPUT 4
43: U SHORT_BINSTRING '1/1/1'
50: q BINPUT 5
52: U SHORT_BINSTRING 'text'
58: q BINPUT 6
60: U SHORT_BINSTRING 'foo is good'
73: q BINPUT 7
75: U SHORT_BINSTRING 'title'
82: q BINPUT 8
84: U SHORT_BINSTRING 'foo'
89: q BINPUT 9
91: u SETITEMS (MARK at 34)
92: b BUILD
93: h BINGET 1
95: ) EMPTY_TUPLE
96: \x81 NEWOBJ
97: q BINPUT 10
99: } EMPTY_DICT
100: q BINPUT 11
102: ( MARK
103: h BINGET 4
105: U SHORT_BINSTRING '2/2/2'
112: q BINPUT 12
114: h BINGET 6
116: U SHORT_BINSTRING 'bar is better'
131: q BINPUT 13
133: h BINGET 8
135: U SHORT_BINSTRING 'bar'
140: q BINPUT 14
142: u SETITEMS (MARK at 102)
143: b BUILD
144: h BINGET 1
146: ) EMPTY_TUPLE
147: \x81 NEWOBJ
148: q BINPUT 15
150: } EMPTY_DICT
151: q BINPUT 16
153: ( MARK
154: h BINGET 4
156: U SHORT_BINSTRING '3/3/3'
163: q BINPUT 17
165: h BINGET 6
167: U SHORT_BINSTRING 'no one likes baz :('
188: q BINPUT 18
190: h BINGET 8
192: U SHORT_BINSTRING 'baz'
197: q BINPUT 19
199: u SETITEMS (MARK at 153)
200: b BUILD
201: e APPENDS (MARK at 5)
202: . STOP
看起来很复杂!但实际上,它并不那么糟糕。pickle
基本上是一个栈机器,你看到的每个 ALL_CAPS 标识符都是一个 opcode,它以某种方式操作内部 "堆栈" 进行解码。如果我们尝试解析一些复杂的结构,这将更加重要,但幸运的是,我们只是在生成一组基本元组的简单列表。所有这些 "代码" 所做的就是在堆栈上构建一堆对象,然后将整个堆栈推入列表中。
我们确实需要关心的一个事情是你看到的 'BINPUT' / 'BINGET' 操作码。基本上,这些用于 '备忘录',以减少数据占用空间,pickle
使用 BINPUT <id>
保存字符串,然后如果它们再次出现,而不是重新转储它们,就简单地使用 BINGET <id>
从缓存中检索它们。
还有另一个复杂性!不仅有 SHORT_BINSTRING
- 对于大于 256 字节的字符串,还有普通的 BINSTRING
,以及一些有趣的 Unicode 变体。我假设你正在使用带有所有 ASCII 字符串的 Python 2。如果这不是正确的假设,请再次评论。
好的,所以我们需要在流中读取文件,直到遇到 '\81' 字节 (NEWOBJ
)。然后,我们需要向前扫描,直到遇到一个 '(' (MARK
) 字符。然后,在遇到 'u' (SETITEMS
) 之前,我们读取键/值字符串对 - 应该总共有 3 对,每个字段一个。
那么,让我们开始吧。这是我用流式方式读取 pickle 数据的脚本。它远非完美,因为我只是为了回答这个问题而将其拼凑在一起,你需要大量修改它,但这是一个很好的开始。
pickledata = '\x80\x02]q\x00(c__main__\nDocument\nq\x01)\x81q\x02}q\x03(U\x04dateq\x04U\x051/1/1q\x05U\x04textq\x06U\x0bfoo is goodq\x07U\x05titleq\x08U\x03fooq\tubh\x01)\x81q\n}q\x0b(h\x04U\x052/2/2q\x0ch\x06T\x14\x05\x00\x00bar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterq\rh\x08U\x03barq\x0eubh\x01)\x81q\x0f}q\x10(h\x04U\x053/3/3q\x11h\x06U\x13no one likes baz :(q\x12h\x08U\x03bazq\x13ube.'
# simulate a file here
import StringIO
picklefile = StringIO.StringIO(pickledata)
import pickle # just for opcode names
import struct # binary unpacking
def try_memo(f, v, cache):
opcode = f.read(1)
if opcode == pickle.BINPUT:
cache[f.read(1)] = v
elif opcode == pickle.LONG_BINPUT:
print 'skipping LONG_BINPUT to save memory, LONG_BINGET will probably not be used'
f.read(4)
else:
f.seek(f.tell() - 1) # rewind
def try_read_string(f, opcode, cache):
if opcode in [ pickle.SHORT_BINSTRING, pickle.BINSTRING ]:
length_type = 'b' if opcode == pickle.SHORT_BINSTRING else 'i'
str_length = struct.unpack(length_type, f.read(struct.calcsize(length_type)))[0]
value = f.read(str_length)
try_memo(f, value, memo_cache)
return value
elif opcode == pickle.BINGET:
return memo_cache[f.read(1)]
elif opcide == pickle.LONG_BINGET:
raise Exception('Unexpected LONG_BINGET? Key ' + f.read(4))
else:
raise Exception('Invalid opcode ' + opcode + ' at pos ' + str(f.tell()))
memo_cache = {}
while True:
c = picklefile.read(1)
if c == pickle.NEWOBJ:
while picklefile.read(1) != pickle.MARK:
pass # scan forward to field instantiation
fields = {}
while True:
opcode = picklefile.read(1)
if opcode == pickle.SETITEMS:
break
key = try_read_string(picklefile, opcode, memo_cache)
value = try_read_string(picklefile, picklefile.read(1), memo_cache)
fields[key] = value
print 'Document', fields
# insert to sqllite
elif c == pickle.STOP:
break
这正确地读取了我的用pickle格式2编写的测试数据(修改为一个长字符串):
$ python picklereader.py
Document {'date': '1/1/1', 'text': 'foo is good', 'title': 'foo'}
Document {'date': '2/2/2', 'text': 'bar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is betterbar is better', 'title': 'bar'}
Document {'date': '3/3/3', 'text': 'no one likes baz :(', 'title': 'baz'}
祝你好运!