average a stream

average.py

streaam = []
P = 100

def SMA(N):
    stream.append(N)
    if len(stream) > P:
        # Only average the last P elements of the stream
        del(stream[:1])
    elif len(stream) == 0:
        average = 0
    else:    
        average = sum(stream.iteritems() / len(stream)
    return average