Python: Beyond the Basics. Brittney White

Transcription

1 Python: Beyond the Basics Brittney White

2 Topics Covered Cursors Geometry objects Leveraging other Python modules

3 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)

4 Data Access Module Cursors

5 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 # fields = [ Name, Year, Count ]

6 Tokens Used as shortcuts in place of field names The value of the ObjectID field. A geometry object for the feature. A tuple of the feature's centroid x,y coordinates. A tuple of the feature's true centroid x,y coordinates. A double of the feature's x-coordinate. A double of the feature's y-coordinate. A double of the feature's z-coordinate. A double of the feature's m-value. The esri JSON string representing the geometry. 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.

7 arcpy.da.searchcursor arcpy.da.searchcursor(in_table, field_names, {where_clause}, {spatial_reference}, {explode_to_points}, {sql_clause})

8 arcpy.da.searchcursor optional where clause parameter

9 # Open a Search Cursor, print results table = "Crime_Incidents_2016" fields = ["Shift", "Offense", "Method", "Ward"] qry = " Ward = '6' " with arcpy.da.searchcursor(table, fields, qry) as cursor: for row in cursor: print("shift: {} Offense:{} Method: {} Ward: {}".format(row[0], row[1], row[2], row[3]))

10 # Open a Search Cursor, print results table = "Crime_Incidents_2016" fields = ["Shift", "Offense", "Method", "Ward"] qry = " Ward = '6' " with arcpy.da.searchcursor(table, fields, qry) as cursor: for row in cursor: print("shift: {} Offense:{} Method: {} Ward: {}".format(row[0], row[1], row[2], row[3]))

11 arcpy.da.updatecursor arcpy.da.updatecursor(in_table, field_names, {where_clause}, {spatial_reference}, {explode_to_points}, {sql_clause}) Method deleterow () updaterow (row) Explanation Deletes the current row Updates the current row in the table.

12 arcpy.da.updatecursor

13 arcpy.da.updatecursor

14 arcpy.da.updatecursor

15 arcpy.da.insertcursor arcpy.da.insertcursor(in_table, field_names) Method insertrow (row) Explanation Inserts a row into a table.

16 arcpy.da.insertcursor

17 arcpy.da.insertcursor

18 arcpy.da.insertcursor

19 Working with Geometry Objects Reading geometries - arcpy.da.searchcursor - arcpy.da.updatecursor Writing geometries - arcpy.da.updatecursor - arcpy.da.insertcursor Work with geoprocessing tools

20 Using geometry as input with geoprocessing tools

21 Demo: Which buffers overlap?

22 Which buffers overlap?

23 Leveraging other Python modules Installed with ArcGIS Pro Examples: arcgis scipy pandas The Python Standard Library Examples: os urllib zipfile Additional thirdparty Python packages Examples: beautifulsoup tensorflow scikit-learn

24 Leveraging other Python modules Python Standard Library - Read a csv with the csv module - Unzip a.zip file with the zipfile module - Download data from the internet with the urllib module - Automatically open an output with the os module - many more Can install other pre-existing Python packages with ArcGIS Pro Python Package Manager

25 Demo: Python Package Manager

26 Print Your Certificate of Attendance Print Stations Located at L Street Bridge Tuesday 12:30 pm 6:30 pm GIS Solutions Expo Hall D Wednesday 10:45 am 5:15 pm GIS Solutions Expo Hall D 5:15 pm 6:30 pm GIS Solutions Expo Social Hall D 6:30 pm 9:00 pm Networking Reception National Building Museum

27 Please Take Our Survey on the App Download the Esri Events app and find your event Select the session you attended Scroll down to find the feedback section Complete answers and select Submit

28 Python Sessions at #FedGIS Session Tuesday Wednesday Python: An Introduction 1:45 pm 2:45 pm in 202B 8:30 am 9:30 am in 202B Python: Beyond the Basics 4:15 pm 5:15 pm in 208AB 11:00 am 12:00 pm in 202B Using Python in ArcGIS Enterprise Python: Building Geoprocessing Tools Data Science in ArcGIS Using Python and R 8:30 am 9:30 am in 201 5:15 pm 6:15 pm in 201 4:00 pm 5:00 pm in 202B Machine Learning in ArcGIS 4:15 pm 5:15 pm in 202 A 8:30 am 9:30 am in 202A