type declaration

assignment2/paxos.py

 # http://pymotw.com/2/SocketServer/
 from functools import total_ordering
+from typing import Dict, Set, Tuple, DefaultDict
+
 from message import *
 import socketserver
 import pickle
@@ -14,24 +16,22 @@ class Paxos(socketserver.TCPServer):
         self.servers = servers                                      # All servers addresses
 
         # Sets up other variables
-        self.is_leader = False                                      # Are we the leader?
-        self.ballot = BallotNumber(1, self.address)                 # Our ballot number
-        self.highest_ballot_seen = BallotNumber(0, self.address)    # Highest ballot number seen
-        self.proposals = dict()                                     # Used by leader to send P2A to acceptors
-        self.accepted = dict()                                      # Used by acceptors in P2A and also P1B
-        self.log = dict()                                           # The log
-        self.leader_recent_ping = False
+        self.is_leader: bool = False  # Are we the leader?
+        self.ballot: BallotNumber = BallotNumber(1, self.address)  # Our ballot number
+        self.highestBallotSeen: BallotNumber = BallotNumber(0, self.address)  # Highest ballot number seen
+        self.proposals: Dict[int, BallotValuePair] = dict()  # Used by leader to send P2A to acceptors, slot number -> proposal
+        self.accepted: Dict[int, BallotValuePair] = dict()  # Used by acceptors in P2A and also P1B, slot number -> proposal
+        self.log: Dict[int, BallotValuePair] = dict()  # The log
+        self.leader_recent_ping: bool = False  # True if we think leader is alive
 
         # for proposal phase
-        self.slot_in = 1                                            # First non-executed proposal slot (+1 last executed slot)
-        self.slot_out = 1                                           # First empty slot (+1 last proposed slot)
-
-        # Multimap equivalent in python is defaultdict: https://stackoverflow.com/questions/1731971/is-there-a-multimap-implementation-in-python
-        self.slot_to_acceptors = defaultdict(set)                   # Used by leader to decide majority for each slot after P2B
+        self.slot_in: int = 1  # First non-executed proposal slot (+1 last executed slot)
+        self.slot_out: int = 1  # First empty slot (+1 last proposed slot)
+        self.slot_to_acceptors: DefaultDict[int, Set[Tuple[str, int]]] = defaultdict(set)  # Used by leader to decide majority for each slot after P2B, Multimap<Integer, Address>
 
         # for leader election
-        self.voters = set()                                         # Yes votes for leader election
-        self.p1b_replies = dict()                                   # Accepted values for each slot by acceptors that voted yes
+        self.voters: Set[Tuple[str, int]] = set()  # Yes votes for leader election
+        self.p1b_replies: Dict[int, BallotValuePair] = dict()  # Accepted values for each slot by acceptors that voted yes, slot number -> proposal
         # ...
 
         # Default leader during setup