I assume you are using this as a fun exercise. As a general warning, I want to add to @Reinderien's comment by linking to this question: why is writing your own encryption-discouraged. This also applies to security software.

Now to the code review. I suggest you salt the storage, If I read this correctly, the same user and password combination will lead to the same entry, telling an attacker that you reused your password. Salting means adding something to your data soup, so it does not all taste the same. In praxis, that means adding some random data to the info before encrypting.

I assume you are using this as a fun exercise. As a general warning, I want to add to @Reinderien's comment by linking to this question: why is writing your own encryption-discouraged. This also applies to security software.

Now to the code review. I suggest you salt the storage, If I read this correctly, the same user and password combination will lead to the same entry, telling an attacker that you reused your password. Salting means adding something to your data soup, so it does not all taste the same. In praxis, that means adding some random data to the info before encrypting.

Edit: More possible problems: python has garbage collection. What problems does this cause for securing passwords during and after the runtime of your program? what could you do about it?

every import is a possible source of insecurities. do you really need an additional library? why not tk-inter? see also this article on pypi's code signatures

does your code make any effort to ensure it has not been altered between executions?

there is no input sanitation, a altered db could easily do injections.