Rhino 8 Python Components Error: "no module named 'ladybug'"

I have installed ladybug-core library, but when I try to use the ladybug library in the Rhino 8 Script Editor (or a Rhino 8 Python component), I am getting an error “no module named ‘ladybug’”, What am I doing wrong?


Hi @Gowtham ,

I changed some things about your question since you originally said that you were using GHPython but it’s clear from your screenshot that you are NOT using GHPython.

GHPython is the Grasshopper Python editor that was used through Rhino 7 and can still be accessed in Rhino 8 by double-clicking the Grasshopper canvas and typing #GhPython Script:

If you have Ladybug Tools installed and you type from ladybug.epw import EPW in an actual GHPython component, it will work out of the box no matter what your version of Rhino is. However, it will not work out of the box in the Rhino 8 “Python 3 Script” or the “IronPython 2 Script” components:

The new “Python 3 Script” and “IronPython Script” components that @eirannejad added to Rhino 8 use completely separate Python environments from GhPython. So, if you want to use Ladybug Tools SDK in those other environments, you have to make sure that the dependency paths of those other environments know where Ladybug Tools SDK is installed on your system. Luckily @eirannejad added a very elegant way to do this, which just involves adding comments at the top of your script to specify the script’s dependencies.

There are many different ways that you can use comments to specify the script’s dependencies, which @eirannejad outlines here on the McNeel foum. But my preference is to do it with the following line of code, which works if you have installed Ladybug Tools SDK via the Pollination single-click installer in it’s default location:

# env: C:\Program Files\ladybug_tools\python\Lib\site-packages

So just add that to the top of your “Python 3 Script” and “IronPython Script” components and everything will work:

I hope that helps.


@gotham You can add the ladybug search path to the Python search paths in the options window:


@chris The Ladybug installer can drop a file in ~/.rhinocode or any of the directories listed in the page below to automatically add search paths to either python 3, 2, or both:


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Thanks, @eirannejad .

That’s really good to know that there’s a way to add our installation folder to the Python path without needing to add the comment at the top of each script. Granted, I think this comment system that you set up is really nice and I still recommend that people use it. It makes the dependencies of the script explicit and, as the Zen of Python goes, “explicit is better than implicit.”

But we can consider having our installers add the LBT installation folder to the search paths per your suggestion.

I can test this myself but, if the ~/.rhinocode folder has not yet been initialized for a given user but we try to create the folder during our installation process with just the .pth file in it, will this .pth file be used when the rhinocode folder eventually gets initialized? If so, that gives us a reliable way to easily add it to the Python paths for everyone and maybe we can say that people don’t have to put the dependency comment at the top of their scripts if they don’t want to. Otherwise, this method might not be the most reliable and I’m still going to recommend that everyone use the comment system.

Yes and the .rhinocode folder is one of the many options for where the .pth files can be located.

Thank you so much !!! I did not know about Gh PythonScript

Thanks @eirannejad ,

I see that, even if the Python environment has not been initialized in Rhino 8, I can still write the .pth files into an otherwise empty .rhinocode folder. They’ll be ignored the first time that the Python environment is initialized but, after restarting Rhino, I can import Ladybug Tools without needing the comment.

Given all of this, I’ll make a tweak to our installers so that we write these .pth files in to the .rhinocode folder or we create the folder if it does not yet exist. This way, people have access to the Ladybug Tools SDK in these other environments if they want.

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FYI, @eirannejad ,

I just added a method that will run as part of our single-click installer, which will write (or append to) the .pth files in the .rhinocode folder:

This way, people using the Rhino 8 ScriptEditor or Rhino 8 Python components will be able to import all of the Ladybug tools core libraries from their installation without needing to add any header comments to their scripts.

And, even though all of the Ladybug Tools components are still GHPython and will be for a while until our community is predominantly using Rhino 8 (or 9 in the future), making this change now will hopefully set up some good practices of just using the one (latest) version of the LBT core libraries that come with our installation. For example, this should help prevent dependency conflicts down the line of people having one version of the LBT core libraries living in the .rhinocode folder (pip installed via some comment in a script) and another “official” version of the LBT core libraries living with their Ladybug Tools installation.

@eirannejad ,
Am I correct that search paths specified in these python-2.pth and python-3.pth files will take precedence over duplicate copies of packages found in:




If so, that is great and I’m sure that this will save users of the ScriptEditor many headaches of having an old copy of the core libraries loaded and not knowing why they are missing a certain Ladybug Tools feature.

Short answer is No. The site-packages folder is added by python engine during initialization and is one of the first folders on the search path stack.

.pth overrides show up after default python paths but before any environment created by RhinoCode for the script.

Let me know if you have any ideas on how we can improve.