variable creation

[Justin Azoff]

Alistair King wrote:
> Hei all,
>
> im trying to create a list of variables for further use:
[snip]
> this works to a certain extent but gets stuck on some loop. Im a
> beginner and am not sure where im going wrong.

You are trying to do too much in one function.  Split those loops up
into a few little ones and the program will work... or if it doesn't,
you'll know exactly where the problem is.

def get_element(pt):
    "Return None or a single element from the periodic table"
    while 1:
        el = raw_input("Which element would you like to include? ")
        if not el: #blank answer
            return
        if el in pt:
            return pt[el]
        print "This element is not in the periodic table, please try
again"

def get_elements(pt):
    elements = []
    while 1:
        el = get_element(pt)
        if not el:
            break
        elements.append(el)

    return elements

See how using two separate functions makes it easy to test?
In [10]:print get_element(pt)
Which element would you like to include? X
This element is not in the periodic table, please try again
Which element would you like to include? H
1.0079400000000001

In [11]:print get_elements(pt)
Which element would you like to include? Z
This element is not in the periodic table, please try again
Which element would you like to include? Li
Which element would you like to include? B
Which element would you like to include? H
Which element would you like to include?
[6.9409999999999998, 10.811, 1.0079400000000001]


Now, since the information for a single element consists of more than
just a single number, you'll probably want to make a class for them.
Once you have an object for every element, you can add them to a class
for the periodic table.

-- 
- Justin