Storing and calling program file data via pickle

Question

I'm trying to save my data to a file via pickle. Whenever I run my program, the data never seems to loads to 'thelist'.

import pickle

thelist = []

thelist.append(input('Input: '))

def save_data():
    with open('thelist.data', 'wb') as filehandle:
        pickle.dump(thelist, filehandle)
        print('Data saved.')

def load_prev_data():
    try:
        with open('thelist.data', 'rb') as filehandle:
            thelist = pickle.load(filehandle)
    except FileNotFoundError:
        print('No data found. Starting new session.')

load_prev_data()
save_data()

print(thelist)

I haven't tried JSON, but I'm trying to get an idea of if this would even work. I know the answer is probably staring me in the face, but I'm hoping someone can help. If anyone can point me in the right direction, it would be greatly appreciated. Thank you.

Answer 1

You create local variable thelist and you should use return to send it outside function

def load_data():
    try:
        with open('thelist.data', 'rb') as filehandle:
            data = pickle.load(filehandle)
    except FileNotFoundError:
        print('No data found. Starting new session.')
        data = []

    return data

and

thelist = load_data()

Similar way you could get list as argument when you save it

def save_data(data):
    with open('thelist.data', 'wb') as filehandle:
        pickle.dump(data, filehandle)
        print('Data saved.')

and

save_data(thelist)

---

Full code:

import pickle

# --- functions ---

def load_data():
    try:
        with open('thelist.data', 'rb') as filehandle:
            data = pickle.load(filehandle)
    except FileNotFoundError:
        print('No data found. Starting new session.')
        data = []

    return data

def save_data(data):
    with open('thelist.data', 'wb') as filehandle:
        pickle.dump(data, filehandle)
        print('Data saved.')

# --- main ---

thelist = load_data()

thelist.append(input('Input: '))

print(thelist)

save_data(thelist)