String, variable ?

[iqgrisskinka]

Hello

I'm trying to make a chemistry-program that's going to calculate the mass of an group of atoms.

It is however hard to make it work. First I give C a value of 12 and O a value of 6. To this point everything is fine, but now I want to be able to write CO2 and have the program understand that it's supposed to take the value of C and add it to the value of O times two.

Do you have any idea on how I should do?

[bvdet]

My suggestion is to write a function that would parse your chemical designations and return the total. Let's assume a notation like "C.0^2" where "." is a delimiter for the elements and "^" is a delimiter for the atom quantity of the previous element.

Example:

def molecule_mass(molecule):
    massDict = {"C": 12, "O": 16, "Ca": 40, "Uut": 284}
    mass = 0
    elementList = molecule.split(".")
    for item in elementList:
        if "^" in item:
            atom, n = item.split("^")
            mass += massDict[atom] * int(n)
        else:
            mass += massDict[item]
    return mass


print molecule_mass("C.O^2.Ca")

The above prints "84".

[iqgrisskinka]

Bad

Well, there's no input... It just gives you the answer 84

[bvdet]

I am assuming you have some basic level of Python knowledge. It is not appropriate for me to write a complete solution for you.