Available with Business Analyst license.
Summary
Generates competitive advantage trade areas for each store by creating boundary lines equidistant from each of the store locations.
Illustration

Usage
- The spatial reference of the output feature class will be the same as the store layer. 
- The store layer input feature class must be point features. 
- In most cases, the store layer input feature layer will be a Business Analyst store layer. 
- Selecting all sites to use will create rings for each point feature in the ring centers (stores) input feature class. 
- In ArcMap, trade areas will only be created for features that are within the active study area or analysis extent. 
- There must be at least two store points in the input store layer for this tool to work. 
Syntax
ThiessenPolygons_ba (StoreLayer, StoreIDField, All_Or_Single_Or_Selected, OutputFeatureClass, {ByID_Or_ByName}, {Single_Site})| Parameter | Explanation | Data Type | 
| StoreLayer | The input feature class containing center points for the Thiessen polygons. In most cases, this will be a Business Analyst store layer. | Feature Layer | 
| StoreIDField | Unique ID field in the polygon center (store) layer. | Field | 
| All_Or_Single_Or_Selected | Defines how to create polygons for points in the input feature layer. 
 | String | 
| OutputFeatureClass | The feature class that will contain the polygon features. | Feature class | 
| ByID_Or_ByName (Optional) | Field used to select a single point. 
 | String | 
| Single_Site (Optional) | ID or name of store to be used as the single point. | String | 
Code sample
ThiessenPolygons example (stand-alone script)
# Name: ThiessenPolygons.py
# Description: Creates Thiessen based trade areas around selected stores. 
# Author: Esri
# Import system modules
import arcview
import arcpy
arcpy.ImportToolbox(r"C:\Program Files (x86)\ArcGIS\Desktop10.7\Business Analyst\ArcToolbox\Toolboxes\Business Analyst Tools.tbx")
# Acquire extension license 
arcpy.CheckOutExtension("Business") 
 
# Define input and output parameters for the Thiessen Polygons tool
StoreLayer = "C:/temp/sf_stores.shp"
StoreIDField = "STORE_ID"
All_Or_Single_Or_Selected = "ALL"
OutputFeatureClass = "C:/temp/ThiessenPolygons.shp"
ByID_Or_ByName = ""
Single_Site= ""
 
# Create Thiessen Polygon based trade areas
arcpy.ThiessenPolygons_ba(StoreLayer, 
						StoreIDField, 
						All_Or_Single_Or_Selected, 
						OutputFeatureClass, 
						ByID_Or_ByName,
						Single_Site)
 
# Release extension license 
arcpy.CheckInExtension("Business")
Environments
This tool does not use any geoprocessing environments.
Licensing information
- ArcGIS Desktop Basic: Requires Business Analyst
- ArcGIS Desktop Standard: Requires Business Analyst
- ArcGIS Desktop Advanced: Requires Business Analyst