CODEWITHSUNDEEP
pythonpickle
qingxin
qingxin

Reputation: 1

i dump a self-define class object by pickle,but sometimes i can not load it back

i build a toy distributed DB. the transaction of this db is like this: 

class Handle(object):
def __init__(self,fragment_no,table,key,data):
    self.fragment_no=fragment_no
    self.data=data
    self.table=table
    self.key=key
def __setstate__(self,state):
    self.fragment_no,self.table,self.key,self.data=state
def __getstate__(self):
    return (self.fragment_no,self.table,self.key,self.data)
class Transaction(object):
def __init__(self,fragment_no,t_id,tran_type="a"):
    self.t_id=t_id
    self.fragment_no=fragment_no
    self.t_handles=[]
    self.checksum=""
    self.tran_type=tran_type
def add_handle(self,handle):
    self.t_handles.append(handle)
def compute_checksum(self):
    self.checksum=""
def test_checksum(self):
    return True
def is_valiad(self):
    pass
def __setstate__(self,state):
    self.t_id,self.t_handles,self.fragment_no,self.tran_type,self.checksum=state
def __getstate__(self):
    return (self.t_id,self.t_handles,self.fragment_no,self.tran_type,self.checksum)
class RemoteTransaction(Transaction):
"""
state consist of:
    cordinator:begin,ask,commit(abort),end
    particapant:begin,replayed,end
"""
def __init__(self,dbt_id,fragment_no=0,t_id=0,tran_type="a"):
    Transaction.__init__(self, fragment_no, t_id, tran_type)
    self.state="begin"
    self.dbt_id=dbt_id
def set_data(self,fragment_no,t_id):
    self.fragment_no=fragment_no
    self.t_id=t_id
def __setstate__(self,state):
    self.state,self.dbt_id,self.t_id,self.t_handles,self.fragment_no,self.tran_type,self.checksum=state
def __getstate__(self):
    return (self.state,self.dbt_id,self.t_id,self.t_handles,self.fragment_no,self.tran_type,self.checksum)

and at the commit part the code is 

f=open("./"+str(self.port)+"/database/"+str(tran.fragment_no)+"/journal/"+str(tran.t_id),"wb")
pickle.dump(tran,f)
f.close()
file=open("./"+str(self.port)+"/database/"+str(tran.fragment_no)+"/journal/"+str(tran.t_id),'rb')
c=pickle.load(file)

sometimes this code work. but when the transaction has two handle this part of code may break here is the state of transaction when it breakdown,(i use print(tran.getstate() func)):

(1, [<Journal.transaction.Handle object at 0x03D3F7D0>, <Journal.transaction.Handle object at 0x03D3F950>], 1, 'a', '')

the error is that: faultString: str: :state is not a dictionary

Upvotes: 0

Views: 138

Answers (1)

Wolph
Wolph

Reputation: 80031

Your __getstate__ method is returning a tuple, not a dictionary. That is most likely your issue here. While you can have a custom __getstate__ and __setstate__ which use a tuple, by default Python uses dictionaries for the state (specifically, it returns self.__dict__).

So if you have older objects pickled (before your __getstate__) they would have stored __dict__ instead of your tuple.

Upvotes: 1

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