Python: Getting Started Ben Ramseth [email protected] @esriMapNinja E M E R A L D SAPPHIRE THANK YOU TO OUR SPONSORS Topics covered • What’s is python? • Why use python? • Basics of python • ArcPy • Geoprocessing tools • Other python options What is Python? 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 Why use Python? Why use Python with ArcGIS • Automate repetitive tasks • Develop custom tools • Add geoprocessing to web applications • Customize Desktop apps • Extend the capabilities of ArcGIS Basics of Python Where do I write Python scripts? • Python file is text with .py extension • Python window in ArcGIS • Best to use IDE - Integrated Development Environment 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 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 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 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 Python Demo Basics ArcPy ArcPy • ArcGIS Python site package • Introduced in ArcGIS 10.0 - 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 ArcGIS Desktop and ArcGIS Pro Python versions • ArcGIS Desktop uses • ArcGIS Pro uses Python Python 2.7 3.x 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 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 Running geoprocessing tools with Python 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) 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” 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 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 Python error handling • Try…Except - Try to do something, and if an error occurs, do something else - Like… - Print(arcpy.GetMessages()) ArcPy functions • Perform useful tasks - List data: - ListFeatureClasses - Get data properties: - Describe • Enables automation of manual tasks 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) 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) 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 ArcGIS API for Python Script against a portal ArcGIS Python API vs ArcPy ArcGIS Python API ArcPy • Script against a portal • ArcGIS Desktop - ArcGIS Online or ArcGIS Enterprise - ArcMap – Python 2.7 - Python 3.5 - ArcGIS Pro – 3.5 • Analysis, Portal Admin, Content • Mostly geoprocessing Creation, Big Data Analysis • Some map automation Four different groups working with the ArcGIS Python API - Org Administrators - Content Publishers - GIS Analysts and Data Scientists - Power Users/Developers 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 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 Questions? 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