split create_new_address, so that get_new_address can be used without the context of a wallet

lib/wallet.py

@@ -531,20 +531,23 @@ class Wallet:
     
 
     def create_new_address(self, for_change):
+        n = len(self.change_addresses) if for_change else len(self.addresses)
+        address = self.get_new_address(n, for_change)
+        if for_change:
+            self.change_addresses.append(address)
+        else:
+            self.addresses.append(address)
+        self.history[address] = []
+        return address
+        
+    def get_new_address(self, n, for_change):
         """   Publickey(type,n) = Master_public_key + H(n|S|type)*point  """
         curve = SECP256k1
-        n = len(self.change_addresses) if for_change else len(self.addresses)
         z = self.get_sequence(n, for_change)
         master_public_key = ecdsa.VerifyingKey.from_string( self.master_public_key, curve = SECP256k1 )
         pubkey_point = master_public_key.pubkey.point + z*curve.generator
         public_key2 = ecdsa.VerifyingKey.from_public_point( pubkey_point, curve = SECP256k1 )
         address = public_key_to_bc_address( '04'.decode('hex') + public_key2.to_string() )
-        if for_change:
-            self.change_addresses.append(address)
-        else:
-            self.addresses.append(address)
-
-        self.history[address] = []
         print address
         return address