Introduction to GIS Programming and Fundamentals with Python and ArcGIS®

Chaowei Yang

• Publisher: CRC Press
• Year: 2017
• ISBN:
  9781466510104
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Ingegneria civile

Combining GIS concepts and fundamental spatial thinking methodology with real programming examples, this book introduces popular Python-based tools and their application to solving real-world problems. It elucidates the programming constructs of Python with its high-level toolkits and demonstrates its integration with ArcGIS Theory. Filled with hands-on computer exercises in a logical learning workflow this book promotes increased interactivity between instructors and students while also benefiting professionals in the field with vital knowledge to sharpen their programming skills. Readers receive expert guidance on modules, package management, and handling shapefile formats needed to build their own mini-GIS. Comprehensive and engaging commentary, robust contents, accompanying datasets, and classroom-tested exercises are all housed here to permit users to become competitive in the GIS/IT job market and industry.

Section II

Python Programming

3

Introduction to Python

Learning a programming language is a practical and progressive journey. You will begin with the basics, and gradually increase your skills at complex coding. This chapter will introduce fundamental Python components, including classes and objects, syntax, data types, operators, functions, flow control, exceptions, input/output, and modules. A number of libraries are available for specific development, including graphical user interfaces, databases, Internet, and web programming. To facilitate the learning process, you will utilize your understanding of GIS to start building a mini-GIS package while learning the programming language.

3.1Object-Oriented Support

One of Python’s most important characteristics is object-oriented structure. Foundational Python programming requires understanding concepts about classes and objects, inheritance, composition, package, and class sharing. Python provides the mechanism to define a class and create objects from that class.

Classes and objects are widely used in Python. Objects are instances of classes. Objects have attributes and methods. Dot(.) refers to attributes and methods of an object. In Chapter 2, this book defined Point class and created p1 as a point object. You can use p1.x and p1.calDis() to call the attribute and method of the object. Inheritance helps you reuse the attributes and methods of a class (superclass) by using the super class to define new classes in the format ‘class subclass (superclass)’. All public and protected attributes and methods are inherited by subclasses automatically. Private attributes and methods will not be inherited. For example, three vector classes (Point, Polyline, and Polygon) are defined by inheriting the Feature class’s method draw() as detailed in Chapter 2. Composition helps maintain the part–whole relationship, where one object of a class includes objects of other classes. Python uses object reference to implement the composition relationship. As discussed in Chapter 2, a list of points are used to keep the coordinates of a polyline or polygon border.

When classes and met...