Calculate area of geometry in hectares using ArcPy

Question

I have the following script, where it adds fields to a shapefile. The fields are a code and "Sup_ha", which is the area in hectares:

import arcpy

shapefile = "path/shapefile"
CODE_TEST = "2022"

arcpy.AddField_management(shapefile, "CODE", "TEXT", 10, "", "", "refcode", "NULLABLE", "REQUIRED")

cur = arcpy.UpdateCursor(shapefile) 
for row in cur :
    row.setValue("CODE", CODE_TEST)
    cur.updateRow(row)


arcpy.AddField_management(shapefile, "SUP_HA", "DOUBLE", 10, 2, "", "refcode", "NULLABLE", "REQUIRED")

The result is as follows:

In the field "SUP_HA" I need to calculate the area in hectares. What code should go after what is shown?

Answer 1

First off, I would reccomend using a with statement when implementing your cursors. The with statement will automatically close your cursor when the code exits the code block, freeing up the resources used by the cursor. as to exactly how you calculate the area into hectares will depend on the units the shapefile is currently in. In the code below, I have assumed that your shapefile is in meters.

import arcpy

shapefile = "path/shapefile"
CODE_TEST = "2022"

# Add CODE field
arcpy.AddField_management(shapefile, "CODE", "TEXT", 10, "", "", "refcode", "NULLABLE", "REQUIRED")

# Update CODE field with CODE_TEST value
with arcpy.da.UpdateCursor(shapefile, ["CODE"]) as cur:
    for row in cur:
        row[0] = CODE_TEST
        cur.updateRow(row)

# Add SUP_HA field
arcpy.AddField_management(shapefile, "SUP_HA", "DOUBLE", 10, 2, "", "refcode", "NULLABLE", "REQUIRED")

# Calculate area in hectares and update SUP_HA field
with arcpy.da.UpdateCursor(shapefile, ["SHAPE", "SUP_HA"]) as cur:
    for row in cur:
        # Get geometry of shapefile
        geom = row[0]
        # Calculate area in hectares
        area_ha = geom.area / 10000 # 1 hectare is equal to 10000 square meters. Change the calculation in this line if geom.area is not in square meters
        # Update SUP_HA field with calculated area
        row[1] = area_ha
        cur.updateRow(row)

The second cursor will access the geometry of your shapefile in the units it currently is in, and calculate the conversion in to hectares (again, assuming the area is in square meters)