[Tutor] Choosing between dictionary or external file

[Alan Gauld]

On 28/06/17 17:44, Henrique C. S. Junior wrote:

> using dictionaries to store information. Here is an example:
> 
> ........................
> basis_sets = {
>     "Pople-style basis sets": {
>         "3-21G": "Pople 3-21G (H-Cs)",
>         "STO-3G": "Minimal basis set(H-I)",
>         "3-21GSP": "Buenker 3-21GSP (H-Ar)",
>         "4-22GSP": "Buenker 4-22GSP (H-Ar)",
>         "6-31G": "Pople 6-31G and its modifications (H-Zn)",
>         "m6-31G": "Modified 6-31G for 3d transition metals (Sc-Cu)",
>         "6-311G": "Pople 6-311G and its modifications (H-Br)"},
> 
>     "The def2 basis sets of the Karlsruhe group": {
>         "def2-SVP": "Valence double-zeta basis set with 'new' polarization
> ........................
> 
> My question is: is this the correct approach? The dictionaries, after
> finished, probably will not have to be changed for a long time and my idea
> is to import them in the main code.

Using dictionaries is ok, but your keys are inordinately long.
I'd probably define the strings as a set of variables(consts)
that can then be used in the dictionaries and in your code.

Otherwise you are likely to wind up with horrible looking code like:

if "beunker" in lower(basic_sets["Pople-style basis sets"]["3-21GSP"]):
    .....

Which is verbose at the very least and likely to be
error prone too. Whereas if you define something like

POPLE = "Pople-style basis sets"
...
basic_sets = {POPLE: {....}}

The code becomes

if "beunker" in lower(basic_sets[POPLE]["3-21GSP"]):
   ...

Which, I think, is slightly easier on the eye. (And
you can still use the longhand version if you think
you need it)

> A second question is regarding the creation os a GUI, what are your
> recommendations (keeping in mind that I'm not an experienced programmer)
> Glade, PyQt + QT Designer, Tkinter or something else (to run on Linux, Mac
> and Windows)?

For easy to learn wrapping of a CLI I'd suggest Tkinter but
if you want to distribute the code to others then Qt probably
looks nicer and has more features. But a steeper learning
curve.

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos