Please leave attributions in so we know who is saying what.
Matt D wrote:
> [Ramit Prasad wrote]
> > [Peter Otten wrote]
> >
> > 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`.
> >
>
> I put this like this:
>
> class DataEvent(wx.PyEvent):
> # the values of the text fields get passed into the constructor
> inside of data
> def __init__(self, data):
> wx.PyEvent.__init__(self)
> # this line *binds* this class to a certain type of event,
> wxDATA_EVENT
> self.SetEventType (wxDATA_EVENT)
> # and this is the actual data
> self.data = data
> with open('mypicklelog.txt','ab') as log: # open in binary mode
> pickle.dump(self.data, log) # serialize data and write to file
>
>
> And I still get nothing. This has me super confused, I have trying at
> this for a long time and I have been reading the docs like
>
> http://docs.python.org/2/library/pickle.html
>
> And I still don't get it to work. So the C++ makes the pickle, this is
> from the comments in the C++ :
>
> /**
> * snapshot_du_handler. Writes traffic snapshots to a msg_queue based
> * on the HDU frame contents. The format used is that of a pickled
> * python dictionary allowing the other end of the queue to pick only
> * those fields of interest and ignore the rest.
> */
>
> Then the python program (attached) program unpickles and repickles it?
> I attached the python program, if you have a minute or two please take a
> look, its not too long.
The problem is that what gets sent across the queue is actually a container
of some kind that has a pickled string. The comments in the code are just
wrong. The key is following display_data which is correct.
# unpickle the string
pickled_dict = message.to_string()
This is actually retrieving a string (or bytes more accurately) OF pickled data
from some message or container object. These bytes then needs to be unpickled.
#separate the string into values for each text control (attrs is a pickle
object)
attrs = pickle.loads(pickled_dict)
Here the pickled data (as bytes/string) are unpickled and attrs
is a Python dictionary (not a "pickle object").
*I use bytes/string interchangeably because in Python 2 they are the same.
In Python 3 and semantically, they are different so the differentiation is
important.
The real question is why do you want this pickle in a file? I am not sure
it will be easy to pull out and reuse anyway. Given your experience level,
I think this is a lot of work for something that you are unlikely to be able
to easily use. I think it would be more useful to `log.write(repr(attrs))`.
Once you have the bytes of pickled data, just write that to file.
with open('mypicklelog.txt','ab') as log:
# All pickles will run together because there is no spacing.
log.write(self.data.to_string())
Again, I think you would be better off with the repr()
with open('mypicklelog.txt','ab') as log:
log.write(repr(pickle.loads(self.data.to_string())))
~Ramit
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