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December 11, 2013 / stevebaer

ghPython – New component and parallel modules

Just in time for Christmas… ghPython was released this week and it has two new features that I’m really excited about.

Download ghPython…

A little background

David Rutten was visiting the McNeel Seattle office in November to discuss future work on Grasshopper and Rhino. When David is in town it always gives me the chance to brainstorm with him and try to solve some of the features that users ask for. Two features that we commonly hear about are “how can I do what X component does, but through RhinoCommon/code?” and “how can I improve performance on my computer with many CPUs?”

Out of these chats came the two major new features in ghPython; the ability to call components from python and an easy way to do this using multiple threads. ghPython ships with a new package (ghpythonlib) that supports these two new features.

Components As Functions (node-in-code)

There is a module in ghpythonlib called components which attempts to make every component available in python in the form of an easy to call function. Here’s a sample to help paint the picture.

import ghpythonlib.components as ghcomp

# call Voronoi component with input points
curves = ghcomp.Voronoi(points)
# call Area component with curves from Voronoi
centroids = ghcomp.Area(curves).centroid

Notice that the above sample is just three lines of script (and two lines of comments to help describe what is happening.)
GH_Binary_32 Here is a sample gh file


Of course you can mix in other python to perform calculations on the results of the component function calls. I tweaked the above example to find the curve generated from Voronoi that has the largest area.

import ghpythonlib.components as ghcomp

curves = ghcomp.Voronoi(points)
areas = ghcomp.Area(curves).area
#find the biggest curve in the set
max_area = -1
max_curve = None
for i, curve in enumerate(curves):
    if areas[i] > max_area:
        max_area = areas[i]
        max_curve = curve

Remember, this can be done for almost every component in Grasshopper (including every installed add-on component.) I use the term almost because there are cases where the function call doesn’t make sense. These cases are for things like Kangaroo or timers where the state of the component is important between iterations. Fortunately this is pretty rare.

Along with the new functionality that this provides, I also found myself simplifying existing gh definition files by simply lumping together a bunch of related components into a single python script.

Use those CPUs

Along with components is another module in ghpythonlib called parallel. This module has a single function called “run” which takes a list of data as input and a single function that should be called for each item in the list. What the run function does is call this function on as many threads as there are processors in your computer and then properly collect the results so you get a list of return values in the same order as the input list. The return value is whatever your custom function returns. I could show how this is done with the previous samples, but those already run so fast that there is no need to attempt to multithread them. Instead I put together a sample that typically takes around a second to complete on my computer; slicing a brep with 100 planes.

import ghpythonlib.components as ghcomp
import ghpythonlib.parallel

#custom function that is executed by
def slice_at_angle(plane):
    result = ghcomp.BrepXPlane(brep, plane)
    if result: return result.curves

if parallel:
    slices =, planes, True)
    slices = ghcomp.BrepXPlane(brep, planes).curves

GH_Binary_32 Here is a sample gh file

In the above image I’m passing the variable called parallel into the python script with a value of false. This makes the code execute on a single thread and as you can see by the profiler that the performance is the same in the python script as it is just using the BrepXPlane component (which is expected.)
Now when I toggle the input parallel variable to a value of true, the function is executed. This function calls my custom slice_at_angle function 105 times, each time passing in a single plane and all on multiple threads. On my computer with 4 CPUs the execution time drops from one second to 313 milliseconds! A 3X speed boost by just adding a couple lines of script.

Give this new build of ghPython a try. I’m sure there will be questions and probably a bug or two to fix, but it gets fun pretty fast once you get the hang of it.

Downloads for this article


Leave a Comment
  1. heumanndesigntech / Dec 12 2013 1:38 am

    This is AWESOME!
    How do you handle component output variables with spaces in the name?

    • stevebaer / Dec 12 2013 2:07 am

      The autocomplete for functions should provide a description of the input and output names. The results are in the form of a named tuple which means you can access the output using indices like a regular tuple or using names like I show in my samples

      • heumanndesigntech / Dec 12 2013 3:44 pm

        Ah, perfect. thanks!

  2. Jake Hebbert / Dec 12 2013 1:57 am

    Thank you!!!!!!!!!!!

  3. Kristoffer Negendahl / Dec 12 2013 8:00 am


  4. SanderBoer (@SanderBoer) / Dec 12 2013 10:37 am

    Hi Steve,

    A great innovation !
    But do I need to install some other stuff besides the ghpython.gha ? THe autocomplete does not work and the example file above results in this error:

    Runtime error (FormatException): Guid should contain 32 digits with 4 dashes (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx).
    line 105, in __build_module, “C:\Users\sander\AppData\Roaming\McNeel\Rhinoceros\5.0\Plug-ins\IronPython (814d908a-e25c-493d-97e9-ee3861957f49)\settings\lib\ghpythonlib\”
    line 126, in , “C:\Users\sander\AppData\Roaming\McNeel\Rhinoceros\5.0\Plug-ins\IronPython (814d908a-e25c-493d-97e9-ee3861957f49)\settings\lib\ghpythonlib\”
    line 1, in script


  5. SanderBoer (@SanderBoer) / Dec 12 2013 10:47 am

    crossposted this to gh forum, previous post from giulio makes me think a botched sr6 install is the cullprit.

  6. Junyi / Dec 12 2013 5:19 pm

    That’s a great improvement with the access to the gh component!!
    Thanks Steve! Great work!

  7. Jonathan / Dec 12 2013 9:57 pm


  8. issworld / Dec 12 2013 11:39 pm

    I am confused with something:
    “Run” function takes exactly 3 arguments: name of the function, an argument of that function (the one that contains a list) and flatten boolean. The reason why you defined function “slice_at_angle” with only one argument (plane) and just used “brep” as a global variable inside it, is because:
    If you defined “slice_at_angle” with two arguments (brep,plane) both of these would have to be supplied into the “run” function as “run” function represents call for “slice_at_angle” function. And currently run function only supports working on one list, not two? Meaning: second argument from “slice_at_angle” could not be passed?
    I understand that it is pointless to use “brep” input data for multi-threading as it is a just a single surface, not a list. But what happens when we have a grasshopper component that has two or three inputs, both consisted of lists? Then only one of those two inputs could be passed as an argument in the “run” function, right? And again we will define our function (in this case “slice_at_angle”) with one argument too?
    Does this make any sense?

    • stevebaer / Dec 13 2013 12:10 am

      The run function doesn’t really know anything specific about grasshopper. All it does is gets an input list and a function. For every item in the input list, call the function and collect the result. The function receives each item in the list as a the argument. The list could be a list of tuples and in that case each tuple would be passed to the function.

      If you used a different list, say
      items = [brep, planes for plane in planes]

      Then (brep,planes) would be passed as the input argument to the slice function. I hope that makes sense.

      • issworld / Dec 13 2013 12:31 am

        What am I doing wrong?

        import ghpythonlib.components as ghcomp
        import ghpythonlib.parallel
        #custom function that is executed by
        def slice_at_angle(_brep, _planes):
            result = ghcomp.BrepXPlane(_brep, _planes)
            if result: return result.curves
        if parallel:
            items = [(brep, plane) for plane in planes]
            slices =, items, True)
            slices = ghcomp.BrepXPlane(brep, planes).curves
      • stevebaer / Dec 13 2013 12:40 am

        Here’s a better example of what I mean. I’ll use a gist since replying with python scripts here is pretty ugly

  9. issworld / Dec 13 2013 12:54 am

    Thank you

  10. Thorsten / Dec 13 2013 5:23 pm

    Hi Steve,

    I was wondering if I could manage myself to adapt the code to some quite cpu consuming functions we use here, but already stumbled over the first one:
    cap a brep.

    Could you give me a hint what’s wrong?

    import ghpythonlib.components as ghcomp
    import ghpythonlib.parallel
    #custom function that is executed by
    def add_caps_for_open_breps(brep):
        result = ghcomp.CapHoles(brep)
        if result: return result.brep
    if parallel:
        volumes =, brep, True)
        volumes = ghcomp.CapHoles(brep)

    It works for “non-parallel” use, but I get a “line 10” error, “brep is not iterable”.

    • stevebaer / Dec 13 2013 5:31 pm

      Could you post this question at instead? Answering questions with python samples works WAY better over there than here on this wordpress blog. Thanks.

    • stevebaer / Dec 13 2013 6:57 pm

      Are you just passing a single brep into the component or a list of breps? I would also use different variable names so it is clearer what the code is doing. Maybe the input should be “breps” which is what you would pass to you function and then leave the add_caps_for_open_breps function the same because you are working with a single brep from the list.

    • stevebaer / Dec 13 2013 7:06 pm

      Here’s what I came up with (and I get about a 3X speed boost):

      import ghpythonlib.components as ghcomp
      import ghpythonlib.parallel
      def add_caps_for_open_breps(brep):
          return ghcomp.CapHoles(brep)
      if parallel:
          volumes =, breps, True)
          volumes = ghcomp.CapHoles(breps)
  11. diego / Dec 17 2013 6:29 am

    hey steve
    trying to use BlendCurve component with ghpythonlib, i get no error messages, everything sees fine but i get a null result.

  12. diego / Dec 17 2013 6:47 am

    Following on my previous question on the blendCurve component. what am i doing wrong?

    import ghpythonlib.components as ghcomp
    output = ghcomp.BlendCurve(curveA,curveB,1.0,1.0,2)

    • stevebaer / Dec 17 2013 5:02 pm

      Are you setting the Type Hints on the input to curve?

      • diego / Dec 22 2013 2:49 pm

        many thanks steve. that solved the issue. d

  13. Dimitrie Andrei Stefanescu / Dec 17 2013 3:16 pm

    I have a stupid question: why aren’t all the gh components that would benefit from running parallel like this?

    🙂 Really happy to see this, perfect reason to jump on python over the holidays.

    • stevebaer / Dec 17 2013 4:58 pm

      They probably eventually will in Grasshopper 2. What we have right now seems like a great way to prototype multi-threading component code and to find any bottlenecks or bugs in the system.

  14. Ramon / Dec 18 2013 8:50 am

    Hi Steve,
    This is very interesting! Thanks. I do have a question though. In your example 2, when I duplicate the sphere (say 10 times) and graft the results, the Python component in parallel mode is actually three times slower than the original component. Do you get the same behavior?

    • stevebaer / Dec 18 2013 11:49 pm

      Hi Ramon,
      Can you email me the gh definition that you are testing with so I can see exactly what you are testing?

  15. Erick Katzenstein / Feb 9 2014 9:52 pm

    Steve, loving this new functionality! I’m having a little trouble with the ghcomp.Treestatistics() command as it doesn’t seem to return a list of data trees as the Grasshopper Component would. Can you confirm that it’s working on your end?


  16. James Sherman / Mar 10 2014 6:01 pm

    Hi Steve,

    I’m really excited to try out the new parallel processing feature of ghpython, and I actually have a case where it’s application would be perfect. I need to intersect a lot of little mesh cubes with rays, which is a component that takes 8 minutes!!! to run in my Grasshopper script (99% of the total script’s processing time).

    I’m trying to parallelize the MeshRay function, but have had limited success. The parallel python component I wrote performs almost twice as slowly as the native Grasshopper one. I adapted a little test script ( with a much simpler mesh, which shows a performance decrease from the native grasshopper MeshRay. I would have though that dramatically increasing the mesh complexity would show dividends from using the parallel Python component, but it only seems to get worse.

    Do you know if there’s something I’m doing incorrectly?

    Thanks very much for your help! I’ve been over it many times 😦

  17. Mathias Nielsen / Oct 14 2014 1:53 pm

    Hi steve

    I have an array of hourly light measurements throughout a year.

    This gives me an array with {0} .. {1000} as my measure points and (n)=8760 as the length of each list in the array.

    Heres the question, because this computer could really benefit from multicore here.

    How can i split up an operation when looking at those numbers. Let’s say find the maximum value in each point. Or find an hour with the highest value of all my numbers summed up.

  18. Carlos / Feb 29 2016 1:59 pm

    Is it any list to get the names of classes of the GH components… to be called from python?? I really need to get the names of other the intersection components to execute them and call them from a python script, if it is possible. Cheers!

    • stevebaer / Mar 31 2016 11:10 pm

      What intersection components are you referring to? You should get a list of what is available when you hit the period in your script and see an autocomplete list


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  2. ghPython – Outside the Canvas | Steve Baer's Notes
  3. Grasshopper to D3JS | LMNts

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