Python pickle module usage

Question

import pickle
data_list = list()
def Add(x):
 data_list.append(x)
 with open("data.pkl", "wb") as f:
 pickle.dump(data_list, f, pickle.HIGHEST_PROTOCOL)
while 1:
 abc = input("--->")
 if abc == "data":
 with open("data.pkl", "rb") as f:
 print(pickle.load(f))
 else: 
 Add(abc)
 print(data_list)
 

I saved my list with the pickle module. After restarting the program, if I query the list contents without adding new data, I can see the records, but if I add new data, I cannot see the old records. Why i can't see old records ?

Answer 1

It's because you are starting the program with an empty list. you should add a function which sync the database if exists on startup

import os
import pickle
# Sync database
if os.path.exists('data.pkl'):
 with open("data.pkl", "rb") as f:
 data_list = pickle.load(f)
else:
 data_list = list()
def Add(x):
 data_list.append(x)
 with open("data.pkl", "wb") as f:
 pickle.dump(data_list, f, pickle.HIGHEST_PROTOCOL)
while 1:
 abc = input("--->")
 if abc == "data":
 with open("data.pkl", "rb") as f:
 print(pickle.load(f))
 else: 
 Add(abc)
 print(data_list)