<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def init(self):
        "Initialize the message-digest and set all fields to zero."

        self.length = 0L
        self.input = []

        # Load magic initialization constants.
        self.A = 0x67452301L
        self.B = 0xefcdab89L
        self.C = 0x98badcfeL
        self.D = 0x10325476L