Programming in geoinformatics 2017 Theory 8
1 ArcPy module
ArcGIS software comes with a Python module which provides its functionality for use in Python
scripts. You can therefore use ArcPy with any other Python libraries and greatly enhance
ArcGIS capabilities. You can use Python console directly in ArcMap (and test some functions
for example):
Recommendation
ArcPy introduction: http://desktop.arcgis.com/en/arcmap/latest/analyze/arcpy/
a-quick-tour-of-arcpy.htm
Or you can prepare a whole script with desired functionality (e.g. crop all shapefiles in a
folder to a given layer, perform some geospatial operations on top of them and generate a text
file with a report) and add it to ArcGIS as a tool you can use from the Toolbox:
1
Programming in geoinformatics 2017 Theory 8
Do this for tasks you might do frequently for different datasets or tasks you want to automate.
You can then use this toolbox directly from ArcGIS with layers/files/directories you can specify
before running the tool.
Another option is to use ArcPy outside of ArcGIS in a script. You could for example make
a script for collecting data periodically and make it run at 3 A.M. every day, collect data from
a remote location (some server), save it, analyse it and prepare a report. Scientists could use
this to pinpoint some events that are of interest to them.
Note
In ArcGIS Python console, folders in paths have to be escaped – write "\\" or "/" instead
of "\", e.g. "c:\\PGI\\loadAllShapefiles.py" or "c:/PGI/loadAllShapefiles.py"
You use ArcPy like any other Python module, here is an example of a script you can use
from ArcGIS Python console to load all shapefiles in a specified folder:
import arcpy
from arcpy import env
def loadAllShapefiles(path):
# set workspace path to the one we will be searching SHPs in
env.workspace = path
# get a list of all SHPs in the folder
fcList = arcpy.ListFeatureClasses()
print fcList
# sets mxd to the currently opened document
mxd = arcpy.mapping.MapDocument("CURRENT")
# sets df to the first data frame
df = arcpy.mapping.ListDataFrames(mxd, '')[0]
# iterates over every SHP name in the folder
for fc in fcList:
# get the whole path to the SHP
pathToFC = env.workspace + "/" + fc
# create a new layer from the SHP
newLayer = arcpy.mapping.Layer(pathToFC)
# add the new layer to the bottom of the data frame
arcpy.mapping.AddLayer(df,newLayer,"BOTTOM")
# refresh Table of contents and the active view (so the layers appear
immediately when the script finished)→
arcpy.RefreshTOC()
arcpy.RefreshActiveView()
It is then called like this: >>> loadAllShapefiles("c:\\PGI\\")
2
Programming in geoinformatics 2017 Theory 8
An example of a script you run from PyZo, other IDE or command line that clips all features
in a specified directory:
import arcpy
import os
from arcpy import env
# set workspace (where input SHPs are located), output location (where
clipped SHPs will be stored) and the clip feature class→
env.workspace = "c:\\PGI\\in"
outputDir = "c:\\PGI\\out"
clipFC = "c:\\PGI\\jmk.shp"
# get all feature classes in a directory
fcs = arcpy.ListFeatureClasses()
for fc in fcs:
# determine the full name of the output shapefile
outFC = os.path.join(outputDir, fc)
# execute the clip
arcpy.Clip_analysis(fc, clipFC, outFC)
3