topic Re: Create pairs of points in Python Questions

Create pairs of points

AdamForknall — Sun, 03 Jun 2012 23:14:44 GMT

Hi there!

I'm trying to create pairs of point features from a point dataset. I'm not really sure on how to get my for loops working to create only 1 instance of each pair.
For example if I have points A, B, C and D, the final pairs would be AB, AC, AD, BC, BD & CD.

My script in its current state is below - this will print all pairs twice except for those containing the first point in the list, which are only printed once. (I hope that makes sense!)

The ultimate aim is to create a table with XY co-ordinates or geometries of each pair, but at this stage I'm just printing the pairs to screen for checking. I'm a complete python (and programming in general) novice and I'd be really grateful if someone could give me so tips on how to make this happen.

Thanks!
Adam

import arcpy  infc =r"D:\POINTS.shp"  #identify geometry field desc = arcpy.Describe(infc) shapefieldname = desc.ShapeFieldName  #Create primary Search Cursor rows = arcpy.SearchCursor(infc)  pointsList = []   count = 0 #iterator counter for testing  #create a list of the points for row in rows:     feat = row.getValue(shapefieldname)     point = feat.getPart()     pointsList.append(point)  count = 0  for point1 in pointsList:     #print point1.X     for point2 in pointsList[1:]:         if point1 != point2:             print (point1,point2)

Re: Create pairs of points

NobbirAhmed — Sun, 12 Dec 2021 07:11:18 GMT

Modify the last loop as follows:

# make a duplicate of the original point list
tempPointList = pointList[:]

for point1 in pointsList:

    # remove the current point from the temp list
    tempPointList.remove(point1)

    for point2 in tempPointList:
        
        # point1 and point2 to make a pair
        print (point1.X, point2.X)

Re: Create pairs of points

AdamForknall — Mon, 04 Jun 2012 21:54:06 GMT

Genius! Thanks Nobbir!

😄

Re: Create pairs of points

NobbirAhmed — Tue, 05 Jun 2012 05:55:24 GMT

Looks like a simpler and better solution already exists in the standard module (pointed out by Jason Scheirer of Esri Geoprocessing team).

# itertools standard module's combinations function does it clearly import itertools  for point1, point2 in itertools.combinations(pointsList, 2):    print point1.X, point2.X

There is no need to create a duplicate list and iterate over two lists.

Re: Create pairs of points

AdamForknall — Tue, 05 Jun 2012 21:18:36 GMT

Brilliant! That makes the code much simpler. Thanks!