data structure design question

[Felix Thibault]

At 08:07 2/12/00 +0200, Moshe Zadka wrote:
>On Fri, 11 Feb 2000, Felix Thibault wrote:
<snip>
>
>Hmmm...why not have a generic Atom:
>
>h1 = Atom('H', 1)
>
>(actually, the 1 is superfluous: you can have a table mapping name to
>number of electrons on the outer level (is that it?))
>
I was thinking of having a generic class that could initialize with
some optional parameters for stuff like charge or isotope that could
vary from atom to atom, with default and constant values in a table,
like this:

PeriodicTable = { 'H':{'name':'hydrogen', 'valence_electrons': 1,\
		       'mass': 1.0078, 'atomic_number':1}} #more...

class Element:
    
    #set count for each element to zero
    indexes = {}
    for key in PeriodicTable.keys():
        indexes[key] = 0
    del key
    
    def __repr__(self):
        return self.symbol + `self.index`
    
    def __init__(self, symbol, valence_electrons=None):
        self.symbol = symbol
        Element.indexes[symbol] = Element.indexes[symbol] + 1
        self.index = Element.indexes[symbol]
        if valence_electrons is None:
            self.valence_electrons =
                  PeriodicTable[symbol]['valence_electrons']
        else:
            self.valence_electrons = valence_electrons
        self.mass = PeriodicTable[symbol]['mass']
        self.atomic_number = PeriodicTable[symbol]['atomic_number']
        #more...

def reset():
    """reset() set all element counts back to zero"""
    for key in PeriodicTable.keys():
        Element.indexes[key] = 0

def H():
    return Element('H')

class Molecule:
    def __init__(self, bonddict):
        mass = 0
        atoms = bonddict.keys()
        for atom in atoms:
            mass = mass + atom.mass
        self.mass = mass
        self.bonds = bonddict
        self.atoms = atoms

h1, h2 = H(), H()
hydrogen_molecule = Molecule({h1:[h2], h2:[h1]})

<snip>
>> The dictionary method seems more condensed and readable, so I
>> am preferring it right now, even though I would have to make a
>> new instance for every atom of an element
>
>That's a good thing. Every atom *is* a new instance of the atom class.
>
Of course! I won't be stingy with them, then.

Thanks!
 
Felix

>--
>Moshe Zadka <mzadka at geocities.com>. 
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