Grasshopper

algorithmic modeling for Rhino

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!

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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.

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?

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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.

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

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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?

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

Hey djordje!

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

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..

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Hi,

this seems to work for RhinoCommon Point3d objects

newpoints = [ Rhino.Geometry.Point3d( p ) for p in oldpoints ]

Great! That's what I was looking for.


And thank you Anders and Djordje for your helpful advice!

Hey! make sure you understand the difference between shallow copy and deep copy of a list.

I read this python clone list tutorial and it was very easy to understand the difference.

Remeber that copying your list of points could bring issues if you do a shallow copy or unexpected result.

hope it helps!

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