A class named Seizer which helps us to create pickle-like files.

seizer.py

import shelve

class Seizer:
    def __init__(self, filename, writeback=False):
        self.filename = filename
        self.writeback = writeback
        self.last_get = None
        self.last_add = None
        self.open()
    
    def __exit__(self):
       self.close()

    def get_item(self, key):
        if key in self.data_file:
            self.last_get = {key: self.data_file[key]}
            return self.data_file[key]
        else:
            return None

    def add_item(self, key, value):
        self.data_file[key] = value
        self.last_add = {key: value}
        
    def remove_item(self, key):
        del self.data_file[key]
    
    def open(self):
        self.data_file = shelve.open(self.filename, self.writeback)

    def close(self):
        self.data_file.close()