Python pickle module usage

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

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)