Python: Beyond the BasicsBrittney White, Esri

Katie Leaverton, Chesapeake Bay Foundation

Topics Covered

• Cursors

• Geometry objects

• Leveraging other Python modules

• Python in ArcGIS Pro

Cursors

• Used to:

- Iterate over the set of rows in a table

- Insert new rows into a table

• Two varieties

- arcpy.da cursors (10.1 onwards; significantly faster performance)

- “Classic” cursors (provided only for continuing backward compatibility)

Data Access Module Cursors

Required Arguments

• Table

- The feature class, layer, table, or table view

• Fields

- Single field or list of field names

- Index position in fields parameter defines value access

# 0 1 2

fields = [“Name”, “Year”, “Count”]

Tokens

• OID@ —The value of the ObjectID field.

• SHAPE@ —A geometry object for the feature.

• SHAPE@XY —A tuple of the feature's centroid x,y

coordinates.

• SHAPE@TRUECENTROID —A tuple of the feature's true

centroid x,y coordinates.

• SHAPE@X —A double of the feature's x-coordinate.

• SHAPE@Y —A double of the feature's y-coordinate.

• SHAPE@Z —A double of the feature's z-coordinate.

• SHAPE@M —A double of the feature's m-value.

• SHAPE@JSON — The esri JSON string representing the

geometry.

• SHAPE@WKB —The well-known binary (WKB)

representation for OGC geometry. It provides a portable

representation of a geometry value as a contiguous stream

of bytes.

• SHAPE@WKT —The well-known text (WKT) representation

for OGC geometry. It provides a portable representation of

a geometry value as a text string.

• SHAPE@AREA —A double of the feature's area.

• SHAPE@LENGTH —A double of the feature's length.

Used as shortcuts in place of field names

arcpy.da.SearchCursor

arcpy.da.SearchCursor(in_table, field_names,

{where_clause}, {spatial_reference},

{explode_to_points}, {sql_clause})

arcpy.da.SearchCursor

arcpy.da.SearchCursor

arcpy.da.SearchCursor

Demo: Search

Cursor with

csv module

arcpy.da.UpdateCursor

arcpy.da.UpdateCursor(in_table, field_names,

{where_clause}, {spatial_reference},

{explode_to_points}, {sql_clause})

Method Explanation

deleteRow () Deletes the current row

updateRow (row) Updates the current row in the table.

arcpy.da.UpdateCursor

arcpy.da.UpdateCursor

arcpy.da.UpdateCursor

arcpy.da.InsertCursor

arcpy.da.InsertCursor(in_table, field_names)

Method Explanation

insertRow (row) Inserts a row into a table.

arcpy.da.InsertCursor

arcpy.da.InsertCursor

arcpy.da.InsertCursor

Working with Geometry Objects

• Reading geometries

- arcpy.da.SearchCursor

- arcpy.da.UpdateCursor

• Writing geometries

- arcpy.da.UpdateCursor

- arcpy.da.InsertCursor

• Work with geoprocessing tools

Python in ArcGIS Pro

• Changes to functionality in arcpy

• Upgrade to Python 3

- print statement function

- print('This will print safely in Python 2 and 3')

• Conda

Using GIS and Python to Save Time and Save the Bay

Collected Data

Program: Baltimore Harbor Study Center

Vessels: Snowgoose

General Locations: Fort Carroll, Port of Baltimore, Patapsco River, Baltimore Chesapeake Bay

Collection Methods Used: Otter trawls and oyster hand scrapes

SPECIES NAME MARCH APRIL MAY JUNE JULY AUG SEPT OCT NOV DEC TOTAL

Alewife

American Eel

American Shad

Atlantic Menhaden

Bay Anchovy

Black Crappie

Black Drum

Black Sea Bass

Blenny

Blue Crab

Blue Crab(bushels)

Blue Fish

Blueback Herring

Bluegill

Bullhead

Butterfish

Carp

Reported Data

Python and Model Builder

Python Script 1: Combines and reformats tables for reporting1. Populate fields for month and year

2. Join the sample table to the species table

3. Pivot the table

4. Add fields for missing months

5. Summarize the total number of each species caught by month, year, and program

6. Calculate Simpsons Diversity Index

7. Create feature class showing where each species is collected

Python and Model Builder

Python Script 1: Combines and reformats tables for reporting1. Populate fields for month and year

2. Join the sample table to the species table

3. Pivot the table

4. Add fields for missing months

5. Summarize the total number of each species caught by month, year, and program

6. Calculate Simpsons Diversity Index

7. Create feature class showing where each species is collected

Python and Model Builder

Python Script 1: Combines and reformats tables for reporting

Python and Model Builder

1. Populate fields for month and year

2. Join the sample table to the species table

3. Pivot the table

4. Add fields for missing months

5. Summarize the total number of each species caught by month, year, and program

6. Calculate Simpsons Diversity Index

7. Create feature class showing where each species is collected

Python Script 1: Combines and reformats tables for reporting1. Populate fields for month and year

2. Join the sample table to the species table

3. Pivot the table

4. Add fields for missing months

5. Summarize the total number of each species caught by month, year, and program

6. Calculate Simpsons Diversity Index

7. Create feature class showing where each species is collected

Python and Model Builder

Python Script 1: Combines and reformats tables for reporting1. Populate fields for month and year

2. Join the sample table to the species table

3. Pivot the table

4. Add fields for missing months

5. Summarize the total number of each species caught by month, year, and program

6. Calculate Simpsons Diversity Index

7. Create feature class showing where each species is collected

Python and Model Builder

Python Script 1: Combines and reformats tables for reporting1. Populate fields for month and year

2. Join the sample table to the species table

3. Pivot the table

4. Add fields for missing months

5. Summarize the total number of each species caught by month, year, and program

6. Calculate Simpsons Diversity Index

7. Create feature class showing where each species is collected

Python and Model Builder

Python Script 1: Combines and reformats tables for reporting1. Populate fields for month and year

2. Join the sample table to the species table

3. Pivot the table

4. Add fields for missing months

5. Summarize the total number of each species caught by month, year, and program

6. Calculate Simpsons Diversity Index

7. Create feature class showing where each species is collected

Python and Model Builder

Python Script 1: Combines and reformats tables for reporting1. Populate fields for month and year

2. Join the sample table to the species table

3. Pivot the table

4. Add fields for missing months

5. Summarize the total number of each species caught by month, year, and program

6. Calculate Simpsons Diversity Index

7. Create feature class showing where each species is collected

Python and Model Builder

D = Ʃ n(n-1)N(N-1)

n = total number of organisms of a particular speciesN = total number of organisms of all species

Python Script 1: Combines and reformats tables for reporting1. Populate fields for month and year

2. Join the sample table to the species table

3. Pivot the table

4. Add fields for missing months

5. Summarize the total number of each species caught by month, year, and program

6. Calculate Simpsons Diversity Index

7. Create feature class showing where each species is collected

Python and Model Builder

Python Script 2: Get filtered header information

Program: Baltimore Harbor Study Center

Vessels: Snowgoose

General Locations: Fort Carroll, Port of Baltimore, Patapsco River, Baltimore Chesapeake Bay

Collection Methods Used: Otter trawls and oyster hand scrapes

SPECIES NAME MARCH APRIL MAY JUNE JULY AUG SEPT OCT NOV DEC TOTAL

Alewife

American Eel

American Shad

Atlantic Menhaden

Bay Anchovy

Black Crappie

Black Drum

Black Sea Bass

Blenny

Blue Crab

Blue Crab(bushels)

Blue Fish

Blueback Herring

Bluegill

Bullhead

Butterfish

Python and Model Builder

Python and Model Builder

Python and Model Builder

Web Application

Resources for getting started

•http://esriurl.com/FedGISPython

Additional Python Sessions

• Python: Building Geoprocessing Tools (146 B)

- Tuesday 4:00pm

• Advanced Map Automation with Python (146 B)

- Tuesday 5:15pm

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