class BufferFullException(Exception):

pass

class BufferEmptyException(Exception):

pass

class CircularBuffer(object):

def __init__(self, capacity):

self.capacity=capacity

self.buffer=[]

def read(self):

if not self.buffer:

raise BufferEmptyException("BufferEmptyException")

else:

self.out= self.buffer[0]

del(self.buffer[0])

return self.out

def write(self, data):

if len(self.buffer)<self.capacity:

self.buffer.append(data)

else:

raise BufferFullException("BufferFullException")

def overwrite(self, data):

if len(self.buffer)==self.capacity:

del(self.buffer[0])

self.buffer.append(data)

else:

self.buffer.append(data)

def clear(self):

self.buffer=[]