Question about pickle

[Phu Sam]

I have a method that opens a file, lock it, pickle.load the file into a
dictionary.
I then modify the status of a record, then pickle.dump the dictionary back
to the file.

The problem is that the pickle.dump never works. The file never gets
updated.

def updateStatus(self, fp, stn, status):
          f = open(fp, 'rw+')
          fcntl.flock(f.fileno(),fcntl.LOCK_EX | fcntl.LOCK_NB)

          tb = pickle.load(f)

          self.modifyDict(tb, stn, status)

          pickle.dump(tb, f)

          fcntl.flock(f.fileno(),fcntl.LOCK_UN)
          f.close()


What could be the problem here?
What mode should I use to open the file to allow both pickle.load and
pickle.dump?

Thanks,


Phu
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