Graphical User Interfaces (GUIs) In general, Python isn't much used for user interfaces, but there's no reason for not doing so. Build up WIMP (Windows; Icons; Menus; Pointers) Graphical User Interfaces (GUIs). The default package to use is TkInter. This is an interface to the basic POSIX language Tcl ("Tickle", the Tool Command Language) and its GUI library Tk. Also more native-looking packages like wxPython: https://www.wxpython.org/

Basic GUI import tkinter root = tkinter.Tk() # Main window. c = tkinter.Canvas(root, width=200, height=200) c.pack() # Layout c.create_rectangle(0, 0, 200, 200, fill="blue") tkinter.mainloop() # Wait for interactions.

Event Based Programming Asynchronous programming, where you wait for user interactions. In Python, based on callbacks: where you pass a function into another, with the expectation that at some point the function will be run. You register or bind a function with/to an object on the GUI. When an event occurs, the object calls the function.

Simple event import tkinter def run(): pass root = tkinter.Tk() menu_bar = tkinter.Menu(root) root.config(menu=menu_bar) model_menu = tkinter.Menu(menu_bar) menu_bar.add_cascade(label="Model", menu=model_menu) model_menu.add_command(label="Run model", command=run) tkinter.mainloop() We will come back to event based programming when we look at JavaScript.

The user experience Many people design for geeks. Users learn by trying stuff - they rarely read manuals, so think carefully about what the default behavior of any function should be. We need to design for the general public, but make advanced functions available for those that want them. We should try to help the user by... Using familiar keys and menus (e.g. Ctrl + C for copy). Including help systems and tutorials.

Designing for users At every stage when designing the GUI, think "is it obvious what this does?" Make all screens as simple as possible. Turn off functionality until needed, e.g.: model_menu.entryconfig("Run model", state="disabled") # Until the user has chosen files, then: model_menu.entryconfig("Run model", state="normal") Hide complex functionality and the options to change defaults in ‘Options’ menus. Most of all consult and test. There is a formal element of software development called 'usability testing' in which companies watch people trying to achieve tasks with their software.