In continuing to expand our basic datastore functionality and achieve feature parity with more complex systems, it's time to implement CRUD operations—which stands for Create, Retrieve, Update, and Delete. A simple Python datastore class, BasicDataStore, maintains these internal states using a dictionary.

• create: This operation takes a unique key and a value. It adds the key-value pair to the store if the key does not exist already.

• retrieve: It accepts a key and returns the corresponding value from the store. If the key does not exist, it returns None.

• update: This method takes a key and a new value. If the key exists in the store, it updates the value. If the key does not exist, it returns False.

• delete: This operation removes a key-value pair from the store given a key. If the key does not exist, it returns False.

We are using IBM's stock price as an example to illustrate these operations. We create a record for IBM with a price, retrieve it, update it, delete the record, and try to retrieve it again which returns None now.

This is a basic implementation of CRUD operations for our datastore. It resembles how more sophisticated datastores handle these functionalities internally mapping them to complex data manipulations.

xxxxxxxxxx

class BasicDataStore:

    def __init__(self):

        self.store = {}

    def create(self, key, value):

        if key not in self.store:

            self.store[key] = value

            return True

        return False

    def retrieve(self, key):

        return self.store.get(key, None)

    def update(self, key, value):

        if key in self.store:

            self.store[key] = value

            return True

        return False

    def delete(self, key):

        if key in self.store:

            del self.store[key]

            return True

        return False

​

if __name__ == '__main__':

    datastore = BasicDataStore()

    print(datastore.create('IBM', 140.63))  # True

    print(datastore.retrieve('IBM'))        # 140.63

    print(datastore.update('IBM', 141.14))  # True

    print(datastore.delete('IBM'))          # True

    print(datastore.retrieve('IBM'))        # None