exchanging basic python types between separate python components

Currently, if I output an IronPython 'dict' object from a script component, it is automatically converted into a list of strings (each item being one of the keys).

Is there a way I can pass a dict object to another python scripting component?

I know that if I write my own class, I can pass that object to another scripting component, and any Grasshopper Panel component would probably list it by calling its __str__() method.

What built-in methods are being accessed to interpret/cast the output of the Python component? __iter__()?

Replies to This Discussion

Permalink Reply by Benjamin Golder on March 4, 2012 at 2:48pm

I did find a simple work around:

class GhPythonDictionary(object): def __init__(self, pythonDict=None): if pythonDict: self.d = pythonDict else: self.d = {} def ToString(self): return 'GhPythonDictionary object'

Permalink Reply by Benjamin Golder on March 4, 2012 at 2:57pm

This also illustrates something interesting to me:

Where and when are class declarations necessary?

If I have a set of classes that I want to use in a variety of GhPython components,

can I simply make one GhPython component that stores all the class definitions, and then reference the same classes in other scripts that run in the same grasshopper definition?

Are all multiple GhPython components in the same Grasshopper definition running on the same python engine instance? What does that imply for namespaces within python scripts?

Permalink Reply by Benjamin Golder on March 4, 2012 at 3:04pm

I was able to answer most of these questions myself.

It seems that a new GhPython component has no trouble reading instance objects of custom classes that are input, and even provides Intellisense for their attributes, but I cannot access variables declared in another GhPython component.

Is there perhaps a way to access a global namespace for all the python components within a single Grasshopper definition? So that I could purposely declare a class and then instantiate it in other GhPython components? Just curious ...

Permalink Reply by Giulio Piacentino on March 5, 2012 at 6:38am

Hi Benjamin,

you can pass class definitions and use them, sure. Or add them to the sticky variable, for example:

import scriptcontext scriptcontext.sticky["someName"] = someThing

Attached a slightly larger example.

- Giulio
_______________
giulio@mcneel.com

Attachments:

pass-class-definition.ghx, 41 KB

Permalink Reply by Benjamin Golder on March 5, 2012 at 7:11am

so 'sticky' is a dictionary that I can toss variables into! nice! Thank you

Permalink Reply by Giulio Piacentino on March 5, 2012 at 6:40am

Hi Benjamin,

any object that is .Net enumerable will be rendered as a "Grasshopper list" in Grasshopper.
Items exposed in Grasshopper will be the iteration elements. The fact that dict shows this behavior means that if you iterate it, it will give all its keys.

- Giulio
_______________
giulio@mcneel.com

Permalink Reply by Benjamin Golder on March 5, 2012 at 7:11am

Thanks Giulio

How might I override the IEnumerable interface to define this relationship for new classes? Can I just use __iter__(self)?

Permalink Reply by Giulio Piacentino on March 5, 2012 at 7:14am

You normally would inherit from it. I haven't tried but please let me know if you need a sample. The easiest thing, though, is probably just to pass a list or a tuple, as they already implement that interface so they are already treated as "Grasshopper lists".

- Giulio
_______________
giulio@mcneel.com

Permalink Reply by Maverick_n13 on February 29, 2016 at 7:09am

Dear Giulio,

I'm trying to call GH components from python, to see if it is possible running in parallel cores, the operations for "mesh¦ray" intersection operations. I don't know how to get their names and add them to the code. Is it any way I could get them??

I'm starting into this thing of programming in python, and I think you call them "Class" or "Kernel" just correct me if I'm wrong.

Thanks

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