Ive made a program to track my barbell lifts. The code I’ve shown below is opening up a serialized pickle dictionary called users, and if users is empty it prompts the user to create a profile.

import pickle
#used to serialize objects

class Trainee():
    def __init__(self, measurement, benchpress, press, squat, deadlift, weight):
        #parameters of the user
        self.measurement = measurement
        self.benchpress = benchpress
        self.press = press
        self.squat = squat
        self.deadlift = deadlift
        self.weight = weight

with open('users.pickle', 'rb') as f:
    pickled_users = pickle.load(f)
    #read in the pickled users list

while True:
    if not pickled_users:
        #if no account is associated with the user, prompts to create a new profile
        
        greeting = 'Welcome! Lifts Tracker is a program created by Matthew Johnson thatn'
        greeting +='lets users track their big four barbell lifts progression.n'
        greeting +='These are the bench-press, press, squat, and deadlift.n'
        greeting +='To get started, please choose a username: '
        username = str(input(greeting))
        
        message = 'nSelect I for imperial or M for metric [I/M]: '
        reply1 = str(input(message))

        message = 'nEnter your benchpress: '
        reply2 = int(input(message))

        message = 'nEnter your press: '
        reply3 = int(input(message))

        message = 'nEnter your squat: '
        reply4 = int(input(message))

        message = 'nEnter your deadlift: '
        reply5 = int(input(message))

        message = 'nEnter your weight: '
        reply6 = int(input(message))

        pickled_users[username] = Trainee(reply1, reply2, reply3, reply4, reply5, reply6)
        with open('pickled_users', 'wb') as f:
            pickle.dump(pickled_users, f)
        print(pickled_users)
        break

After I run the code in the terminal everything works and it prints the new users profile in pickled users, confirming that it is infact writing to the file. However when I close the program and open it back up again its all gone. What am I doing wrong?