Introduction to Geoprocessing using Python
Introduction to Geoprocessing using Python
Jorge RuizRuiz-Valdepeña
EdUC 2009 Tech Session
1
Geoprocessing options Command line
Dialog Models
ArcObjects
Scripts EdUC 2009 Tech Session
2
Why write scripts? • Automate a work flow – Copy all incoming data into a geodatabase – Perform clip and buffer operations on 1000 data sets
• Run code at specific dates and times – Windows AT command – Windows scheduler – Every Friday print the map
• Easily distribute code – A script is a selfself-contained, single file
• Free up p time for other important p tasks! • Make yourself more efficient
EdUC 2009 Tech Session
3
Why use Python? • Easy to learn! • Free! • Open Open--source, object object--oriented, scripting language – Can view and modify source code – Support pp for large g projects p j – Easy to use
• • • •
Offers Development environments with debugging tools Cross platform and works in many WebWeb-browsers Ability to compile scripts I t ll d with Installed ith ArcGIS A GIS and d ESRI samples l provided id d
EdUC 2009 Tech Session
4
PythonWin • Integrated development environment or IDE • IDE contains menus, toolbars, and context menus – Windows look and feel – All iin one application li ti – Script tools open in PythonWin
• Script window – Write and save code – Autosave A t b f before each h run
• Interactive window – Test lines of code – Report messages
EdUC 2009 Tech Session
5
Statements • The Th print i t statement t t t • Type print ‘Hello’ in the Script window
• Then Th click li k the th Run R button b tt • Prints Hello in the Interactive window
EdUC 2009 Tech Session
6
Comments • • • •
Comment: A nonnon-executable line of code Helps you remember Helps others decipher Lets you add notes – One pound sign (#) for green and italicized – Two pound signs (##) for grey
# # # #
Date: August 3, 2008 P Purpose: T To b buffer ff a f feature t class l This code will contain … This code was written by …
EdUC 2009 Tech Session
7
Variables • Variables are dynamically typed – No declaration keyword – No type assignment – Make up a name and set it equal to a value
fc = “C: C:\ \\Data Data\ \\SanDiego SanDiego\ \\Streets.shp Streets.shp””
• Variables are case sensitive scale = 10000 Scale = 20000
Two different variables
• Variables can hold different data types – Strings, numbers, lists, files, and more
EdUC 2009 Tech Session
8
Decisions • Testing conditions
if x == 1: print "x is 1" elif x == 2: print "x x is 2" 2 else: print "x is not 1 or 2" • Colons used at end of each condition • Indentation defines what executes for each condition – Python y automatically y indents when y you p press Enter – Use tabs or spaces, must be consistent
• Two equal signs for conditions, one for assignment
EdUC 2009 Tech Session
9
Loops • While x = 5 while x < 10:
print x x = x + 1
• Colons end each statement • Indentation defines what executes
EdUC 2009 Tech Session
10
Loops • While x = 5 while x < 10:
print x x = x + 1
• Counted for x in range(1,5): print x
EdUC 2009 Tech Session
11
Loops • While x = 5 while x < 10:
print x x = x + 1
• Counted for x in range(1,5): print x
• List x = [1 [1, 2 2, 3] for a in x: print a
EdUC 2009 Tech Session
12
Common ArcObjects • ArcGIS is built with a set of ArcObjects Application Map Document Feat re Feature
Map
Layer
EdUC 2009 Tech Session
13
More ArcObjects • Scripting doesn’t get to User Interface objects • Which objects can you get to?
Selection
Symbol
Field
Row
Feature Class EdUC 2009 Tech Session
14
Object Model Diagram • Map of geoprocessing objects, properties, and methods
EdUC 2009 Tech Session
15
Object Model Diagram • Map of geoprocessing objects, properties, and methods
EdUC 2009 Tech Session
16
Syntax for properties and methods • Set a property’s value Object.Property = Value gp Workspace = "C:\ gp.Workspace "C:\\temp"
EdUC 2009 Tech Session
17
Syntax for properties and methods • Set a property’s value Object.Property = Value gp Workspace = "C:\ gp.Workspace "C:\\temp"
• Get a property’s value x = Object.Property x = gp.Workspace k print "The workspace name is " + x
EdUC 2009 Tech Session
18
Syntax for properties and methods • Set a property’s value Object.Property = Value gp.Workspace = "C:\ "C: C:\ C: \\temp temp"
• Get a property’s value x = Object.Property x = gp gp.Workspace p print "The workspace name is " + x
• Use a method Object.Method (arg, arg, arg, arg, …) gp.Buffer_analysis (fc fc, , " "C: C:\ \\temp temp\ \\buff.shp", buff.shp", 100)
• Parentheses around arguments • Arguments separated by commas
EdUC 2009 Tech Session
19
Create a geoprocessor object in code • Geoprocessor can be used in any COM language – Component object model language – Perl, Perl VBScript VBScript, JScript JScript,, Python, Python VBA VBA, VB VB, and C# C#
• arcgisscripting module
You access all geoprocessing functionality y through g this variable
– ESRI ESRI--written – Cross Cross--platform
• 9.3 Argument – accept p and return common Python y structures such as lists and Booleans
EdUC 2009 Tech Session
20
Create a geoprocessor object in code in previous versions
• The Python win32com module must be loaded using the Import command. command – This module enables the COM IDispatch communication within Python.
You access all geoprocessing functionality through this variable
EdUC 2009 Tech Session
21
The Buffer tool • Syntax Buffer_analysis (in_features in_features, , out_feature_class, out_feature_class, buffer distance or field, line_side buffer_distance_or_field, buffer_distance_or_field line side, line_end_type line_side, line end type, line_end_type, dissolve_option, dissolve_option , dissolve_field) dissolve_field)
• Example gp.Workspace gp Workspace = "C:\\Database Database\ \\World World" " gp.Toolbox = "Analysis" gp.Buffer("Lakes.shp", gp.Buffer ("Lakes.shp", "BuffLakes.shp", "100 feet feet") ")
• Notes – If units not specified, input feature class units used – If specifying units, make the argument a string
EdUC 2009 Tech Session
22
Syntax If I want to use the UNION tool, how would I know that the inputs are separated by semicolons?
1. ArcGIS Desktop Help 2. If help is not detailed enough, export the tool from a model to a script
EdUC 2009 Tech Session
23
Multiple tools • Run many tools in succession • Use one tool’s output as another’s input # Find a location for a new hotel that must be > 10000 ft # from an existing one and within 2000 ft of a freeway.
gp.Workspace = "C:\\Database Database\ \\SanDiego.mdb SanDiego.mdb" " # B Buffer ff F Freeways
gp.Buffer_analysis("Freeways", gp.Buffer_analysis ("Freeways", " "BuffFreeways BuffFreeways", ", 2000) # Select the Inns
gp.Select_analysis gp gp.Select_analysis( Select analysis(" analysis( ("MajorAttractions MajorAttractions", MajorAttractions ", , "HolidayInns HolidayInns", ", "[NAME] LIKE 'HOLIDAY INN*'") # Buffer the Inns
gp.Buffer_analysis(" gp analysis y ("HolidayInns HolidayInns", y ", "BuffHolidayInns "BuffHolidayInns", y ", 10000) # Erase the buffered Inn areas from the Freeways buffer
gp.Erase_analysis(" gp.Erase_analysis ("BuffFreeways BuffFreeways", ", " "BuffHolidayInns BuffHolidayInns", ", "SuitableAreas SuitableAreas") i bl ") )
EdUC 2009 Tech Session
24
Cursors • Get or edit rows and values in a table • SearchCursor reads values in a row • UpdateCursor makes changes to row values and deletes rows • InsertCursor is used to insert new rows
EdUC 2009 Tech Session
25
Geometry cur = gp.SearchCursor ("Climate") row = cur.Next cur.Next() () while row: geom = row.Shape print geom.Area print geom.Extent row = cur.Next cur.Next() () cur cu
row
geom
EdUC 2009 Tech Session
26
Resources • Web site: www.python.org – Tutorials, Documentation, Forums
• Python books – Learn to Program Using Python, Python, by Alan Gauld – Learning g Python y ((2nd Edition), ), by y Mark Lutz and David Ascher – Python Essential Reference (2nd Edition), by David M. Beazley – The Quick Python Book, Book, by Daryl Harms and Kenneth McDonald – Python Programming on Win32, Win32, by Mark Hammond and Andy Robinson
EdUC 2009 Tech Session
27
Get a free 45 45--minute hands hands--on lesson at the Hands--On Learning Center Hands Topics include: • Introduction to ArcGIS Desktop • Creating C ti a Map M In I ArcGIS A GIS • Basics of the Geodatabase Model • and more Location: ESRI Showcase
EdUC 2009 Tech Session
Jorge RuizRuiz-Valdepeña
EdUC 2009 Tech Session
1
Geoprocessing options Command line
Dialog Models
ArcObjects
Scripts EdUC 2009 Tech Session
2
Why write scripts? • Automate a work flow – Copy all incoming data into a geodatabase – Perform clip and buffer operations on 1000 data sets
• Run code at specific dates and times – Windows AT command – Windows scheduler – Every Friday print the map
• Easily distribute code – A script is a selfself-contained, single file
• Free up p time for other important p tasks! • Make yourself more efficient
EdUC 2009 Tech Session
3
Why use Python? • Easy to learn! • Free! • Open Open--source, object object--oriented, scripting language – Can view and modify source code – Support pp for large g projects p j – Easy to use
• • • •
Offers Development environments with debugging tools Cross platform and works in many WebWeb-browsers Ability to compile scripts I t ll d with Installed ith ArcGIS A GIS and d ESRI samples l provided id d
EdUC 2009 Tech Session
4
PythonWin • Integrated development environment or IDE • IDE contains menus, toolbars, and context menus – Windows look and feel – All iin one application li ti – Script tools open in PythonWin
• Script window – Write and save code – Autosave A t b f before each h run
• Interactive window – Test lines of code – Report messages
EdUC 2009 Tech Session
5
Statements • The Th print i t statement t t t • Type print ‘Hello’ in the Script window
• Then Th click li k the th Run R button b tt • Prints Hello in the Interactive window
EdUC 2009 Tech Session
6
Comments • • • •
Comment: A nonnon-executable line of code Helps you remember Helps others decipher Lets you add notes – One pound sign (#) for green and italicized – Two pound signs (##) for grey
# # # #
Date: August 3, 2008 P Purpose: T To b buffer ff a f feature t class l This code will contain … This code was written by …
EdUC 2009 Tech Session
7
Variables • Variables are dynamically typed – No declaration keyword – No type assignment – Make up a name and set it equal to a value
fc = “C: C:\ \\Data Data\ \\SanDiego SanDiego\ \\Streets.shp Streets.shp””
• Variables are case sensitive scale = 10000 Scale = 20000
Two different variables
• Variables can hold different data types – Strings, numbers, lists, files, and more
EdUC 2009 Tech Session
8
Decisions • Testing conditions
if x == 1: print "x is 1" elif x == 2: print "x x is 2" 2 else: print "x is not 1 or 2" • Colons used at end of each condition • Indentation defines what executes for each condition – Python y automatically y indents when y you p press Enter – Use tabs or spaces, must be consistent
• Two equal signs for conditions, one for assignment
EdUC 2009 Tech Session
9
Loops • While x = 5 while x < 10:
print x x = x + 1
• Colons end each statement • Indentation defines what executes
EdUC 2009 Tech Session
10
Loops • While x = 5 while x < 10:
print x x = x + 1
• Counted for x in range(1,5): print x
EdUC 2009 Tech Session
11
Loops • While x = 5 while x < 10:
print x x = x + 1
• Counted for x in range(1,5): print x
• List x = [1 [1, 2 2, 3] for a in x: print a
EdUC 2009 Tech Session
12
Common ArcObjects • ArcGIS is built with a set of ArcObjects Application Map Document Feat re Feature
Map
Layer
EdUC 2009 Tech Session
13
More ArcObjects • Scripting doesn’t get to User Interface objects • Which objects can you get to?
Selection
Symbol
Field
Row
Feature Class EdUC 2009 Tech Session
14
Object Model Diagram • Map of geoprocessing objects, properties, and methods
EdUC 2009 Tech Session
15
Object Model Diagram • Map of geoprocessing objects, properties, and methods
EdUC 2009 Tech Session
16
Syntax for properties and methods • Set a property’s value Object.Property = Value gp Workspace = "C:\ gp.Workspace "C:\\temp"
EdUC 2009 Tech Session
17
Syntax for properties and methods • Set a property’s value Object.Property = Value gp Workspace = "C:\ gp.Workspace "C:\\temp"
• Get a property’s value x = Object.Property x = gp.Workspace k print "The workspace name is " + x
EdUC 2009 Tech Session
18
Syntax for properties and methods • Set a property’s value Object.Property = Value gp.Workspace = "C:\ "C: C:\ C: \\temp temp"
• Get a property’s value x = Object.Property x = gp gp.Workspace p print "The workspace name is " + x
• Use a method Object.Method (arg, arg, arg, arg, …) gp.Buffer_analysis (fc fc, , " "C: C:\ \\temp temp\ \\buff.shp", buff.shp", 100)
• Parentheses around arguments • Arguments separated by commas
EdUC 2009 Tech Session
19
Create a geoprocessor object in code • Geoprocessor can be used in any COM language – Component object model language – Perl, Perl VBScript VBScript, JScript JScript,, Python, Python VBA VBA, VB VB, and C# C#
• arcgisscripting module
You access all geoprocessing functionality y through g this variable
– ESRI ESRI--written – Cross Cross--platform
• 9.3 Argument – accept p and return common Python y structures such as lists and Booleans
EdUC 2009 Tech Session
20
Create a geoprocessor object in code in previous versions
• The Python win32com module must be loaded using the Import command. command – This module enables the COM IDispatch communication within Python.
You access all geoprocessing functionality through this variable
EdUC 2009 Tech Session
21
The Buffer tool • Syntax Buffer_analysis (in_features in_features, , out_feature_class, out_feature_class, buffer distance or field, line_side buffer_distance_or_field, buffer_distance_or_field line side, line_end_type line_side, line end type, line_end_type, dissolve_option, dissolve_option , dissolve_field) dissolve_field)
• Example gp.Workspace gp Workspace = "C:\\Database Database\ \\World World" " gp.Toolbox = "Analysis" gp.Buffer("Lakes.shp", gp.Buffer ("Lakes.shp", "BuffLakes.shp", "100 feet feet") ")
• Notes – If units not specified, input feature class units used – If specifying units, make the argument a string
EdUC 2009 Tech Session
22
Syntax If I want to use the UNION tool, how would I know that the inputs are separated by semicolons?
1. ArcGIS Desktop Help 2. If help is not detailed enough, export the tool from a model to a script
EdUC 2009 Tech Session
23
Multiple tools • Run many tools in succession • Use one tool’s output as another’s input # Find a location for a new hotel that must be > 10000 ft # from an existing one and within 2000 ft of a freeway.
gp.Workspace = "C:\\Database Database\ \\SanDiego.mdb SanDiego.mdb" " # B Buffer ff F Freeways
gp.Buffer_analysis("Freeways", gp.Buffer_analysis ("Freeways", " "BuffFreeways BuffFreeways", ", 2000) # Select the Inns
gp.Select_analysis gp gp.Select_analysis( Select analysis(" analysis( ("MajorAttractions MajorAttractions", MajorAttractions ", , "HolidayInns HolidayInns", ", "[NAME] LIKE 'HOLIDAY INN*'") # Buffer the Inns
gp.Buffer_analysis(" gp analysis y ("HolidayInns HolidayInns", y ", "BuffHolidayInns "BuffHolidayInns", y ", 10000) # Erase the buffered Inn areas from the Freeways buffer
gp.Erase_analysis(" gp.Erase_analysis ("BuffFreeways BuffFreeways", ", " "BuffHolidayInns BuffHolidayInns", ", "SuitableAreas SuitableAreas") i bl ") )
EdUC 2009 Tech Session
24
Cursors • Get or edit rows and values in a table • SearchCursor reads values in a row • UpdateCursor makes changes to row values and deletes rows • InsertCursor is used to insert new rows
EdUC 2009 Tech Session
25
Geometry cur = gp.SearchCursor ("Climate") row = cur.Next cur.Next() () while row: geom = row.Shape print geom.Area print geom.Extent row = cur.Next cur.Next() () cur cu
row
geom
EdUC 2009 Tech Session
26
Resources • Web site: www.python.org – Tutorials, Documentation, Forums
• Python books – Learn to Program Using Python, Python, by Alan Gauld – Learning g Python y ((2nd Edition), ), by y Mark Lutz and David Ascher – Python Essential Reference (2nd Edition), by David M. Beazley – The Quick Python Book, Book, by Daryl Harms and Kenneth McDonald – Python Programming on Win32, Win32, by Mark Hammond and Andy Robinson
EdUC 2009 Tech Session
27
Get a free 45 45--minute hands hands--on lesson at the Hands--On Learning Center Hands Topics include: • Introduction to ArcGIS Desktop • Creating C ti a Map M In I ArcGIS A GIS • Basics of the Geodatabase Model • and more Location: ESRI Showcase
EdUC 2009 Tech Session
