from StringIO import StringIO
from email.FeedParser import \
    BufferedSubFile, NeedMoreData

fp = StringIO( "1\r\n10\r\n100\r\n"
               "1000\r\n10000\r\n" )
bsf = BufferedSubFile( )
while True:
    data = fp.read( 3 )
    if not data:
        break
    bsf.push( data )
    for line in bsf:
        if line is NeedMoreData:
            break
        print repr( line )
bsf.close()