about socket programming in python

Question

can someone tell me what the [0] after the function calls are? I don't know what they are called so I can't google it

buff = self.socket.recvfrom(1460)[0]
type = struct.unpack('>B', buff[0])[0]
id = struct.unpack('>l', buff[1:5])[0]

Answer 1

In python the postfix [0] is short for .__getitem__(0). It gets the first item in an indexable data structure. In this case self.socket.recvfrom(1460) returns a 2-tuple of (string,address) where string is the bytes received and address is the address of the socket sending the data.