Changing value of layer attribute based on geometrical conditions of line elements through ArcPy in ArcGIS Pro

Question

I have a feature class layer that comprise of line elements. For my purpose, I needed the start and end point coordinates of each line, so I added new columns with add field and use calculate geometry in ArcGIS Pro to assign the start/end coordinates to each line (below table show the attributes).

What I want to do is that to write a python code that compare lines’ first and end coordinates. Then return a list of IDs for those that their start/end points are equal, and append all those as nested lists in a main list. For instance, if object IDs 2, 5 and 6 have same start and end point, and if object IDs 8, 12, 15 an 22 have the same condition, the code return a nested list like this: main_list = [[2, 5, 6], [8, 12, 15, 22]]. Finally, I want to edit the var column with this outcome. I want var to be equal to length of each corresponding nested list minus one. For instance for those example above, var values for object IDs 2, 5 and 6 will be 2 (length of nested list minus one), and for IDs 8, 12, 15 and 22 will be 3.

ID	x_start	y_start	x_end	y_end	var
1
2
.
.

fields = ['ID', 'x_start', 'y_start', 'x_end', 'y_end']
MainList   = [[]]
NestedList = []

ID = [row[0] for row in arcpy.da.SearchCursor(Redundancy_one, ('ID'))]
x_start = [row[0] for row in arcpy.da.SearchCursor(Redundancy_one, ('x_start'))]
y_start = [row[0] for row in arcpy.da.SearchCursor(Redundancy_one, ('y_start'))]
x_end = [row[0] for row in arcpy.da.SearchCursor(Redundancy_one, ('x_end'))]
y_end = [row[0] for row in arcpy.da.SearchCursor(Redundancy_one, ('y_end'))]

i = 0
while i<len(ID):
    with arcpy.da.SearchCursor[Redundancy_one, fields] as cursor:
        for row in cursor:
            if x_start[0] == row[1] and y_start[2] == row[2] and x_end[2] == row[3] and y_end == row[4] and ID[0] =! row[0]:
                NestedList.append(ID[0])
                NestedList.append (row[0])
    MainList.append(NestedList)
    NestedList=[]
    i +=1

Answer 1

You can use pandas and arcpy together

#Create a pandas dataframe from your line layer with the columns ID and the line geometry
import pandas as pd
layer = 'lines_starting_ending_same'
fields = ["ID","SHAPE@"]
df = pd.DataFrame(data=arcpy.da.SearchCursor(layer, fields), columns=["id","line"])

#Calculate start and end coordinates for all lines
df["start_x"]=df.apply(lambda x: x.line.firstPoint.X, axis=1)
df["start_y"]=df.apply(lambda x: x.line.firstPoint.Y, axis=1)
df["end_x"]=df.apply(lambda x: x.line.lastPoint.X, axis=1)
df["end_y"]=df.apply(lambda x: x.line.lastPoint.Y, axis=1)

#Group lines having the same start and end coordinates and list their ids
same_start_and_end = df.groupby(["start_x","start_y","end_x","end_y"])["id"].apply(list).reset_index()

#Count them
same_start_and_end["count"] = same_start_and_end.apply(lambda x: len(x["id"]), axis=1)
same_start_and_end["var"] = same_start_and_end["count"]-1

#Then do whatever you want with the result. For example export as a table, or update the values in your lines table

To create a field in the original table with the calculated var value. Create a dictionary and use it with da.UpdateCursor:

#Create a dictionary with id as key and var as value
update_dict = dict(zip(same_start_end["id"], same_start_end["var"]))
update_dict

#Add an integer field called var
table = r"C:\GIS\data\testdata\lines_starting_ending_same.shp"
arcpy.management.AddField(in_table=table, field_name="var", field_type="SHORT")
#Update it using the dictionary
with arcpy.da.UpdateCursor(table, ["id","var"]) as cursor:
    for row in cursor:
        if row[0] in update_dict:
            row[1] = update_dict[row[0]]
            cursor.updateRow(row)