# An arbitrary collection of objects supported by pickle.
data = {
??? 'a': [1, 2.0, 3, 4+6j],
??? 'b': ("character string", b"byte string"),
??? 'c': set([None, True, False])
}

with open('data.pickle', 'wb') as f:
??? # Pickle the 'data' dictionary using the highest protocol available.
??? pickle.dump(data, f, pickle.HIGHEST_PROTOCOL)

???
with open('data.pickle', 'rb') as f:
??? # The protocol version used is detected automatically, so we do not
??? # have to specify it.
??? data = pickle.load(f)
??? print(str(data))

??? def __init__(self, filename):
??????? self.filename = filename
??????? self.file = open(filename)
??????? self.lineno = 0

??? def readline(self):
??????? self.lineno += 1
??????? line = self.file.readline()
??????? if not line:
??????????? return None
??????? if line.endswith('\n'):
??????????? line = line[:-1]
??????? return "%i: %s" % (self.lineno, line)

??? def __getstate__(self):
??????? # Copy the object's state from self.__dict__ which contains
??????? # all our instance attributes. Always use the dict.copy()
??????? # method to avoid modifying the original state.
??????? state = self.__dict__.copy()
??????? # Remove the unpicklable entries.
??????? del state['file']
??????? return state

??? def __setstate__(self, state):
??????? # Restore instance attributes (i.e., filename and lineno).
??????? self.__dict__.update(state)
??????? # Restore the previously opened file's state. To do so, we need to
??????? # reopen it and read from it until the line count is restored.
??????? file = open(self.filename)
??????? for _ in range(self.lineno):
??????????? file.readline()
??????? # Finally, save the file.
??????? self.file = file
???????
reader = TextReader("hello.txt")
print(reader.readline())
print(reader.readline())
s = pickle.dumps(reader)
#print(s)
new_reader = pickle.loads(s)
print(new_reader.readline())

# the output is
# 1: hello
# 2: how are you
# 3: goodbye