Adding and registering new extension in pystac

[jaiindimple]

I have tried to create a new extension using this script https://github.com/stac-utils/pystac/blob/main/docs/tutorials/adding-new-and-custom-extensions.ipynb. But, facing challenge with registering and adding new STAC extension in pystac. It would be very helpfull if you can you share any other document or script for the same.
Thank You.

@schwehr @lossyrob

[schwehr]

• On what OS are you working?
• What version of python are you using?
• What version of pystac are you using?
• What exacty did you do and what went wrong?

[jaiindimple]

• Working on linux - Ubuntu 18.04.5
• python version - 3.9.4
• pystac version - 0.5.6
• As per this script https://github.com/stac-utils/pystac/blob/main/docs/tutorials/adding-new-and-custom-extensions.ipynb. First i have created new extension and I enabled the new extension and apply it while creating item.json. As given below:
  spectra is the name of extension and pixxel_size is the property

item.ext.enable(Extensions.spectra)
item.ext.spectra.apply(        
        pixxel_size = 10)

Issue comes when i am adding the stac_extensions=[pystac.Extensions.spectra] in pystac.Item while creating item.json

For this i think i need to register the new extension in pystac. For this i need some document and script.
Thank You

@schwehr

[duckontheweb]

@Dimplejain23 Sorry for the confusion around this. The way that extensions are handled was changed in #309 and the instructions for creating a new extension in the notebook that you referenced hasn't caught up yet.

Probably the best example of creating a new extension right now would be to follow the example of #364, which adds the Raster Extension. I will open an issue to track updating those instructions to reflect the new extension system.

[jaiindimple]

@duckontheweb Not able to access the raster extension .py file. Can you please share the link of script and document.
Thank You

[duckontheweb]

@duckontheweb Not able to access the raster extension .py file. Can you please share the link of script and document.
Thank You

That PR was just merged yesterday, so you should be able to access it at pystac/extensions/raster.py now.

The documentation on using extension in the Concepts -> Extensions section of the docs is up-to-date with the new way of using extensions, but the Jupyter notebook that you referenced is not. I'll create a separate issue to track updating that notebook.

[duckontheweb]

I'll create a separate issue to track updating that notebook.

Created #384 to track this.

[duckontheweb]

@Dimplejain23 Were you able to resolve your issues by following the Raster Extension example?

[jaiindimple]

Thank You @duckontheweb, Issue is not yet solved.

[duckontheweb]

Thank You @duckontheweb, Issue is not yet solved.

Thanks for the update.

Just to be clear, there is no longer an ext property on STACObject instances, so the example you posted in the comment above is not expected to work. The equivalent code in the new extension system would probably be something like the following, assuming that you've set up the SpectraExtension class similarly to the Raster Extension example:

# Add the extension's schema URI to the Item
SpectraExtension.add_to(item)

# Creates an extended Item instance
spectra_ext = SpectraExtension.ext(item)

# Apply extension values (this will mutate the underlying item properties)
spectra_ext.apply(pixel_size=10)

If you need more assistance from us, please post a minimal example that we can use to reproduce the problem (including any error tracebacks that you are getting), and I'd be happy to continue to troubleshoot.

[jaiindimple]

Thank You @duckontheweb for the support. I really want to contribute in STAC but as a beginner it takes time for me to grasp the structure.

[duckontheweb]

I can definitely understand that! It's a pretty complicated code base that has seen some big changes recently.

If it would be helpful, I would also be happy to review a PR, even if it is incomplete and not functioning yet. That might be a good way to get some specific feedback on the code and help move you along. Just start the PR title with [WIP] (for example, [WIP] Adds spectra extension, so that we know it's not intended to be merged just yet.

[duckontheweb]

Closing this since the extensions tutorial has been updated and is accurate since #724