问题描述
您为什么会认为附加二进制泡菜会产生单个泡菜?借助酸洗,您可以一个接一个地放置(并取回)多个项目,因此很明显,它必须是“自终止”序列化格式。忘掉台词,把它们找回来!例如:
>>> import pickle
>>> import cStringIO
>>> s = cStringIO.StringIO()
>>> pickle.dump(23, s)
>>> pickle.dump(45, s)
>>> s.seek(0)
>>> pickle.load(s)
23
>>> pickle.load(s)
45
>>> pickle.load(s)
Traceback (most recent call last):
...
EOFError
>>>
只需按一下EOFError
即可告知您完成脱酸处理的时间。
解决方法
我知道这并不是应该使用pickle模块的方式,但是我认为这会起作用。我正在使用Python 3.1.2
这是背景代码:
import pickle
FILEPATH='/tmp/tempfile'
class HistoryFile():
"""
Persistent store of a history file
Each line should be a separate Python object
Usually,pickle is used to make a file for each object,but here,I'm trying to use the append mode of writing a file to store a sequence
"""
def validate(self,obj):
"""
Returns whether or not obj is the right Pythonic object
"""
return True
def add(self,obj):
if self.validate(obj):
with open(FILEPATH,mode='ba') as f: # appending,not writing
f.write(pickle.dumps(obj))
else:
raise "Did not validate"
def unpack(self):
"""
Go through each line in the file and put each python object
into a list,which is returned
"""
lst = []
with open(FILEPATH,mode='br') as f:
# problem must be here,does it not step through the file?
for l in f:
lst.append(pickle.loads(l))
return lst
现在,当我运行它时,它仅打印出传递给该类的第一个对象。
if __name__ == '__main__':
L = HistoryFile()
L.add('a')
L.add('dfsdfs')
L.add(['dfdkfjdf','errree','cvcvcxvx'])
print(L.unpack()) # only prints the first item,'a'!
这是因为看到的是早期EOF吗?也许追加仅适用于ASCII?(在那种情况下,为什么让我执行mode =’ba’?)有没有更简单的方法?