Python: How to make a copy of a list of points

Hi. I'm new to python and I would like to know the easiest way to make a copy of a list of points in a grasshopper python component.

The python way newPointList=oldPointList[:] doesn't seem to work. Which makes sense as a list of point coordinates is a list of lists, isn't it?

That's why I tried:

newpoints=[]
for oldpoint in oldpoints:
newpoint=oldpoint[:]
newpoints.append(newpoint)

But now I get a RuntimeError (see attached file example).

I finally made it work by copying every component of every point in the list seperately. But there has to be a simpler way.

(The example file is about moving a bunch of circles horizontally so that their centers lie on the y-axis.)

Thanks for your advice!

Attachments:

131110_example circles.gh, 7 KB

Replies to This Discussion

Permalink Reply by Anders Holden Deleuran on November 10, 2013 at 8:26am

You should be able to simply use list() like so:

# The original list
list1 = [1,2,3,4]

# Copy the list
list2 = list(list1)

# Change list items
list2[0] = 0
list1[0] = "hu"

# Check result
print list1,list2
print id(list1),id(list2)

There is also a standard Python module for more advanced copy functionality.

Ps. I only got an error in your GH file due to the circles not being internalized (i.e. they were Null). Not quite sure what you are trying to do though.

Permalink Reply by Jonathan Hermann on November 10, 2013 at 8:49am

Thanks a lot!

I made it work with the list() function. This means you always have to convert a list of on3dpoints first into a list of lists and then back to on3dpoints again to get a copy of it.

Did I get that right?

Attachments:

131110_example circles.gh, 7 KB

Permalink Reply by Anders Holden Deleuran on November 10, 2013 at 8:58am

Not sure I follow, on3dpoints is deprecated as far as I know. I have put together a small example of how I would approach your problem (assuming I understood it correctly). See the attached file. I'm using straight up RhinoCommon to construct the circles but you can easily replace that with Rhinoscriptsyntax if you prefer. Also I'm using a pattern where one constructs an empty list and populates this from within a loop instead of first copying the input list.

Attachments:

MoveCirclesToY.gh, 5 KB

Permalink Reply by Anders Holden Deleuran on November 10, 2013 at 9:03am

If you do not need the original circles within the script you could make it even simpler by moving them in-place. See attached.

Attachments:

MoveCirclesToY_Alt.gh, 5 KB

Permalink Reply by Jonathan Hermann on November 10, 2013 at 9:51am

Thanks again. Very helpful and interesting.

Well, the circle issue was more of an example for why I want to copy a list of points than an actual problem...

Anyways. Obviously I have to do some very basic reading (about RhinoCommon for instance).

The .Radius and .Center commands that you applied on the circles: where can I find a list of those?

Permalink Reply by djordje on November 10, 2013 at 12:30pm

Those two are properties for the "Circle" type:
http://4.rhino3d.com/5/rhinocommon/html/AllMembers_T_Rhino_Geometry...

Permalink Reply by Jesus Galvez on November 11, 2013 at 2:54am

Hey djordje!

So you got up to learning Rhinocommon? How is it going? Which language do you code in? Best

Permalink Reply by Anders Holden Deleuran on November 11, 2013 at 3:04am

As Djordje says they are properties of a type (specifically Rhino.Geometry.Circle). This is lingo used in Object Oriented Programming. I wouldn't worry about that too much for now, just know that when you are using geometry types in Grasshopper or Rhino Python you are using classes from the RhinoCommon .NET SDK. I would recommend reading/watching some introductory tutorials (1,2,3) on this subject though, should be enough to build a basic understanding of how RhinoCommon and OOP works.

Regarding accessing information about a type. This is called introspection and Python has some pretty nifty ways of going about it. See the attached example. Hope that helps..

Attachments: