Python: Getting Started. Ben

Transcription

1 Python: Getting Started Ben

2 E M E R A L D S A P P H I R E T H A N K Y O U T O O UR SPONSORS

3 Topics covered What s is python? Why use python? Basics of python ArcPy Geoprocessing tools Other python options

4 What is Python?

5 What is Python? Python is an interpreted, object-oriented, high-level programming. Python's simple, easy to learn syntax emphasizes readability and therefore reduces the cost of program maintenance. Python supports modules and packages, which encourages program modularity and code reuse. Scripting language of ArcGIS Free, cross-platform, easy to learn, widely useful, great community

6 Why use Python?

7 Why use Python with ArcGIS Automate repetitive tasks Develop custom tools Add geoprocessing to web applications Customize Desktop apps Extend the capabilities of ArcGIS

8 Basics of Python

9 Where do I write Python scripts? Python file is text with.py extension Python window in ArcGIS Best to use IDE - Integrated Development Environment

10 Python in an IDE GIS from the comfort of your development environment Integrated Development Environments - Debuggers - Test Frameworks - Coverage - PyLint/pycodestyle - Version Control Integration - Refactoring Tools - Virtual Environment Support - AutoComplete

11 Python in an IDE GIS from the comfort of your development environment Recommended IDEs - PyCharm - Python Tools for Visual Studio - Spyder - Eclipse with PyDev - Wingware

12 Python basics Variable - A name that stores a value; assigned using = Logic for testing conditions - If, else statement - Colon at the end of each condition - Indentation determines what is executed - == tests equality; other operators like >,<,!= Techniques for iterating or looping - While loops, for loops - Colon at end of statement - Indentation determines what is executed

13 Python building blocks Function: - A defined piece of functionality that performs a specific task; requires arguments Module: - a Python file where functions live; import Package: - A collection of related modules Code example - Math.sqrt(100) 10 Python Standard Library / Built-ins - Os, sys, math, datetime, urllib2

14 Python Demo Basics

15 ArcPy

16 ArcPy ArcGIS Python site package Introduced in ArcGIS June 29, 2010 Successor to arcgisscripting module Create tools leveraging ArcGIS - In-Application Geoprocessing Tools and Scripting - Standalone Python Programs 1,000+ ArcPy-based Tools Included in ArcGIS

17 ArcGIS Desktop and ArcGIS Pro Python versions ArcGIS Desktop uses Python 2.7 ArcGIS Pro uses Python 3.x

18 ArcPy in ArcGIS Pro ArcGIS 10.x to ArcGIS Pro - ArcObjects SDK will not move to Pro - Great time to be a Python GIS Developer! - ArcObjects high cost of maintenance and very tightly coupled to COM - Rewrite code in Python 3 in Pro - Platform agnostic vs..net code - Web Services - Vast library of Packages - Improved features in Pro - it s Python and not.net

19 Automating ArcGIS with Python Toolboxes, Python Toolboxes, Interpreters, Command Line, Services Multiple ways to create tools - ArcGIS Toolbox (.tbx) - Python Toolbox (.pyt) - Stand-alone Scripts (.py) - Interactive Python Window Decouple logic code from Toolbox - Testing!! Distutils to create packaged code Sharing Install into tools as needed

20 Running geoprocessing tools with Python

21 Run gp tools Import arcpy Follow tool syntax - Arcpy.toolname_toolboxalias() - Enter input and output parameters How do I use a specific tool? - Tool help page - Copy as Python Snippet - Help(arcpy.Buffer_analysis)

22 Geoprocessing environment settings Use geoprocessing environments as global parameters - See tool help for honored environments Productivity and code cleanup Arcpy.env - Example: arcpy.env.workspace = c:/code

23 Troubleshooting Why do errors occur? - Incorrect tool use, typos, syntax, data already exists My script doesn t work now what! - View geoprocessing messages - Use Python error handling - Debug the script in an IDE

24 Geoprocessing messages Three types of messages - Info, warning, Error Displayed in the Python window Errors displayed in the IDE To see other messages - arcpy.getmessages

25 Python error handling Try Except - Try to do something, and if an error occurs, do something else - Like - Print(arcpy.GetMessages())

26 ArcPy functions Perform useful tasks - List data: - ListFeatureClasses - Get data properties: - Describe Enables automation of manual tasks

27 Batch processing Automating a geoprocessing operation to run multiple times - Clip every feature class in a geodatabase to a boundary - Calculate statistics for every raster in a folder May List functions in ArcPy to perform batch processing Example: - arcpy.env.workspace = c:/data - fclist = arcpy.listfeatureclasses() - for fc in fclist: - print(fc)

28 Getting data properties Describe function reads data properties Returns an object with properties - Data type - Shape type - Spatial reference - Fields Example: - desc = arcpy.describe( c:/data/roads.shp ) - print(desc.shapetype)

29 Python script tools Python script as custom geoprocessing tool Great way to create and share workflows, extend ArcGIS - More accessible the stand-alone Integrated with geoprocessing framework - Use it just like any other tool - Geoprocessing properties and environments - Works with map layers

30 ArcGIS API for Python Script against a portal

31 ArcGIS Python API vs ArcPy ArcGIS Python API Script against a portal - ArcGIS Online or ArcGIS Enterprise - Python 3.5 Analysis, Portal Admin, Content Creation, Big Data Analysis ArcPy ArcGIS Desktop - ArcMap Python ArcGIS Pro 3.5 Mostly geoprocessing Some map automation

32 Four different groups working with the ArcGIS Python API - Org Administrators - Content Publishers - GIS Analysts and Data Scientists - Power Users/Developers

33 Overview of the ArcGIS Python API A Pythonic GIS API Corresponds to best practices Uses standard Python constructs Data structures with clean, readable idioms Easy for a Python programmer to use ArcGIS Easy for an ArcGIS user to script and automate their GIS

34 The Future of Python in ArcGIS Conda integration into ArcGIS - Advanced Python Package Management - Curated channels of scientific Python packages - Includes C and Fortran compiler - Create and host your own conda packages - Easily share your code with the GIS community - Built-In Virtual Environment Support - Manage multiple environments with access to ArcPy - Easily share environments - Trivializes dependency issues

35 Questions?

36