[Tutor] Need help printing a pickled data

[Prasad, Ramit]

Peter Otten wrote:
> Matt D wrote:
> 
> > On 06/24/2013 07:17 PM, Alan Gauld wrote:
> >> On 24/06/13 23:05, Matt D wrote:
> >>> I have been unable to find a way to write pickled data to text file.
> >>
> >> Probably because pickled data is not plain text.
> >> You need to use binary mode. However...
> >>
> >>
> >>>      def __init__(self, data):
> >>>          wx.PyEvent.__init__(self)
> >>>          self.SetEventType (wxDATA_EVENT)
> >>>          # and this is the actual data
> >>>          self.data = data
> >>>          with open('mypicklelog.txt','a') as log:
> >>>              log.write(self.data)
> >>
> >> Since you are not using pickle here, all you are really doing
> >> is trying to write whatever data is to a text file that
> >> happens to have 'pickle' in its name.
> >>
> >> When writing to a text file you need to write strings.
> >> You have no guarantee that 'data' is a string. You should
> >> probably convert it before writing it. Thats one of the
> >> advantages of using real pickles - they take care of
> >> that complication for you.
> >>
> >>> I cant figure out why these last two line dont write to the .txt file
> >>> after the program has received the pickled Python dictionary?
> >>
> >> Pickle data has to be unpickled before you can use it.
> >> Before you can write it back again you need to repickle it.
> >> The code you posted does not show you producing and pickled
> >> data nor indeed you reading any pickled data...
> >>
> >> If 'data' is indeed in pickle format you cannot simply write
> >> it to a text file since Pickle is not in a text format.
> >>
> >>
> > im sorry; some more code will clarify i think ;
> 
> No, you aren't listening to Alan. The suggestive filename notwithstanding
> 
> >         with open('mypicklelog.txt','a') as log:
> >             log.write(self.data)
> 
> will fail unless self.data is a string. Disregarding all other problems for
> the moment, you need
> 
> with open('mypicklelog.txt','ab') as log: # open in binary mode
>     pickle.dump(self.data, log) # serialize data and write to file
> 
> where pickle.dump(obj, file) converts `obj` to a sequence of bytes before it
> is written to `file`.

Well I think self.data is some kind of container with a pickled string, 
given the code to unpickle it is:

       #message is equal to the "data" parameter in the "DataEvent" class
        message = event.data
        # unpickle the string
        pickled_dict = message.to_string()
        #separate the string into values for each text control (attrs is
a pickle object)
        attrs = pickle.loads(pickled_dict)


Try

 with open('mypicklelog.txt','ab') as log: # open in binary mode
     pickle.dump(pickle.loads(self.data.to_string()), log) # serialize data and write to file


~Ramit


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