I need help with a basic database

Hello folks!

So I’m new here, started literally one week ago, about 2-3 hours each day
I love Python but I’m kinda stuck on something
I’m trying to create a user-friendly database about chemical elements’ isotopes, something like this:

Hydrogen = [a, b, c]
Helium = [d, e]
Carbon = [f, g, h]

Where “a”, “b” etc are floats. So far so good, not a big deal


I want something like this:

Step-1: "Please enter the result of your isotopic mass: "
Step-2: (The user gives a value, let’s say f, and it matches Carbon. However, there are more than just one - in this case, “f” - values that are true for Carbon. So, not only f, but also g and h should give away: “It’s Carbon!”) Instead, it gives me error.

My problem is that I just can’t get my code to work with a key with more than just one value

Thanks in advance!

Please post you code and the output when you run it.
That will allow us to help.

Put code and output in between so-called code-fences:

     print("like this")