by Palash Bauri

How to write a simple toy database in Python within minutes

MySQL, PostgreSQL, Oracle, Redis, and many more, you just name it — databases are a really important piece of technology in the progress of human civilization. Today we can see how valuable data are, and so keeping them safe and stable is where the database comes in!

So we can see how important databases are as well. For a quite some time I was thinking of creating My Own Toy Database just to understand, play around, and experiment with it. As Richard Feynman said:

“What I cannot create, I do not understand.”

So without any further talking let’s jump into the fun part: coding.

Let’s Start Coding…

For this Toy Database, we’ll use Python (my favorite ❤️). I named this database FooBarDB (I couldn’t find any other name 😉), but you can call it whatever you want!

So first let’s import some necessary Python libraries which are already available in Python Standard Library:

import jsonimport os

Yes, we only need these two libraries! We need json as our database will be based on JSON, and os for some path related stuff.

Now let’s define the main class FoobarDB with some pretty basic functions, which I'll explain below.

class FoobarDB(object):    def __init__(self , location):        self.location = os.path.expanduser(location)        self.load(self.location)    def load(self , location):        if os.path.exists(location):            self._load()        else:            self.db = {}        return True    def _load(self):        self.db = json.load(open(self.location , "r"))    def dumpdb(self):        try:            json.dump(self.db , open(self.location, "w+"))            return True        except:            return False

Here we defined our main class with an __init__ function. Whenever creating a Foobar Database we only need to pass the location of the database. In the first __init__ function we take the location parameter and replace ~ or ~user with user’s home directory to make it work intended way. And finally, put it in self.location variable to access it later on the same class functions. In the end, we are calling the load function passing self.location as an argument.

. . . .    def load(self , location):        if os.path.exists(location):            self._load()        else:            self.db = {}        return True. . . .

In the next load function we take the location of the database as a param. Then check if the database exists or not. If it exists, we load it with the _load() function (explained below). Otherwise, we create an empty in-memory JSON object. And finally, return true on success.

. . . .     def _load(self):        self.db = json.load(open(self.location , "r")). . . .

In the _load function, we just simply open the database file from the location stored in self.location. Then we transform it into a JSON object and load it into self.db variable.

. . . .    def dumpdb(self):        try:            json.dump(self.db , open(self.location, "w+"))            return True        except:            return False. . . .

And finally, the dumpdb function: its name says what it does. It takes the in-memory database (actually a JSON object) from the self.db variable and saves it in the database file! It returns True if saved successfully, otherwise returns False.

Make It a Little More Usable… 😉

Wait a minute! 😐 A database is useless if it can’t store and retrieve data, isn’t it? Let’s go and add them also…😎

. . . .    def set(self , key , value):        try:            self.db[str(key)] = value            self.dumpdb()            return True        except Exception as e:            print("[X] Error Saving Values to Database : " + str(e))            return False    def get(self , key):        try:            return self.db[key]        except KeyError:            print("No Value Can Be Found for " + str(key))              return False    def delete(self , key):        if not key in self.db:            return False        del self.db[key]        self.dumpdb()        return True. . . .

The set function is to add data to the database. As our database is a simple key-value based database, we’ll only take a key and value as an argument.

First, we’ll try to add the key and value to the database and then save the database. If everything goes right it will return True. Otherwise, it will print an error message and return False. (We don’t want it to crash and erase our data every time an error occurs 😎).

. . . .    def get(self, key):        try:            return self.db[key]        except KeyError:            return False. . . .

get is a simple function, we take key as an argument and try to return the value linked to the key from the database. Otherwise False is returned with a message.

. . . .    def delete(self , key):        if not key in self.db:            return False        del self.db[key]        self.dumpdb()        return True. . . .

delete function is to delete a key as well as its value from the database. First, we make sure the key is present in the database. If not we return False. Otherwise, we delete the key with the built-in del which automatically deletes the value of the key. Next, we save the database and it returns false.

Now you might think, what if I’ve created a large database and want to reset it? In theory, we can use delete — but it's not practical, and it’s also very time-consuming! ⏳ So we can create a function to do this task...

. . . .     def resetdb(self):        self.db={}        self.dumpdb()        return True. . . .

Here’s the function to reset the database, resetdb! It's so simple: first, what we do is re-assign our in-memory database with an empty JSON object and it just saves it! And that's it! Our Database is now again clean shaven.

Finally… 🎉

That’s it friends! We have created our own Toy Database ! 🎉🎉 Actually, FoobarDB is just a simple demo of a database. It’s like a cheap DIY toy: you can improve it any way you want. You can also add many other functions according to your needs.

Full Source is Here 👉 bauripalash/foobardb

I hope, you enjoyed it! Let me know your suggestions, ideas or mistakes I’ve made in the comments below! 👇

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Thank you! See you soon!