Creating Simple

GIS Applications

with Python

Spring 2016

Sam Giebner

Kris Johnson

Outline

Introduction - Tools & Tkinter

    Exercise #1

Classes - Code organization

    Exercise #2

Hooks - Capture user interaction

    Exercise #3

Modules - Connecting the dots

    Exercise #4

What is your experience with Python?

1. A python is a type of snake
2. Dabbled
3. Aspiring apprentice
4. Regular user
5. Snake Charmer

Why create a Python GUI?

A Story about Steve...

Before

After

Tkinter

What is Tkinter?

• Most commonly used GUI toolkit for Python 
• Object-oriented layer on top of Tcl/Tk 

Tkinter Widgets

1. Create widget instance
2. Style widget
3. Place widget

    # Create widget instance     
    new_button = Button(tk_instance)

    # Configure widget
    new_button['text'] = 'Click Here'
    new_button['command'] = do_something()

    # Place widget
    new_button.grid(row=0, column=2)

Classes

Classes

• Blueprint for createing objects

Hooks

Hooks or Callbacks

Capture, tie in user interaction

def callback():
    print "clicked!"

Button(text="click me", command=callback)

def callback(number):
    print "button", number

Button(text="one",   command=lambda: callback(1)).pack()
Button(text="two",   command=lambda: callback(2)).pack()
Button(text="three", command=lambda: callback(3)).pack()

Using a single callback for multiple widgets; lamda allows for passing args to callback

Modules

What is a Module?

• A Python object that you can bind and reference
  • Can contain:
    • Functions
    • Classes
    • Variables
    • Runnable code

What is a Package?

• A collections of related modules

Package

__init__.py

Module.py

Subpackage

__init__.py

Module.py

Python Package Structure

Distributing Your App

Considerations

• Execution

• Dependencies