Update mychain.py

mychain.py

@@ -42,7 +42,8 @@ class Blockchain:
                 'proof': proof,
                 'previous_hash': previous_hash}
         if self.block_valid(block) == True:
-            
+            self.trans_data_out =[]
+
             self.pending_transactions = []
             self.chain.append(block)
             json_object = json.dumps(self.chain, indent=4)