Using from within the browser using pyscript

[Neon22]

I was trying to build a pyscript example that would show local decl,azi for ISS, etc in the browser.

Almost everything comes in but it can't find a python only whl on pypi for the sgp4 dependency.
Are you aware of one ?

Will make a nice demo as it all runs in the browser, caches the packages, uses HTML/CSS for the UI. and maybe webGL on a good day :)

[brandon-rhodes]

@Neon22 — Is pyscript able to do anything with the plain .tar.gz of the source code? If the script inside is run as "python setup.py install", then it should skip compilation if it doesn't have a compiler available, and simply install the Python source code instead.

[Neon22]

Interesting. Maybe... You can upload a zip or wheel and have it unzip but I think it doesn't run setup install.

I think this mech is mainly used as though you were adding raw directories of python code with __init__ etc. the import system is well able to properly pickup a raw package like this without further install tools.

This is why Pypi is the preferred mechanism for pyodide builds. Micropython is much faster/smaller but is a reduced set used by microcontroller is not a full ctypes implementation like pyodide. For Micropython we tend to include all the sep files as (say) rawgithub urls and have it load it without package help. but you can maybe see avoiding some kinds of errors is tricky.

Also has to be pure python code (pyodide project has wrapped a lot of mixed code packages already into wasm form so those ones do all work.)

I'm not entirely certain it won't run in micropython but initially was trying to pyodide as its "all in there".

UPDATE: - it needs numpy and that's only available in pyodide for now. There is a subset mirror for micropython in dev but its in progress...

[Neon22]

OK. created a manual copy of rawgithub links for sgp4 here:

• https://pyscript.com/@neon22/skyfield-starter/latest?files=main.py,pyscript_py.toml,index.html
• runs good :)

You can clone and edit online.

• file references are in pytoml file. They setup where to load from and what it should be called on local filesystem (sandboxed)

So this gets sgp4 in. I think its pretty fast - could time it by importing time and measuring...

What do you think about a python only package of sgp4 - so I could get skyfield in. ??

[brandon-rhodes]

@Neon22 — It took a bit longer to get working than I expected, but I've just tried uploading a pure-Python version of the package:

https://pypi.org/project/sgp4_pure_python/2.24/

I didn't think to change the description, which should really explain that this other version is and point at the main package for the docs, but let's see if it works first. Try it out, and see if it installs in your environment.

[Neon22]

Hmmm. I am still getting the same error - even when forcing to 2.24 ("sgp4==2.24")

• https://pyscript.com/@neon22/skyfield-starter-pkg/latest?files=pyscript_py.toml

Uncaught (in promise) PythonError: Traceback (most recent call last):
File "/lib/python3.12/site-packages/micropip/_commands/install.py", line 146, in install
    raise ValueError(
ValueError: Can't find a pure Python 3 wheel for: 'sgp4==2.24'
See: https://pyodide.org/en/stable/usage/faq.html#why-can-t-micropip-find-a-pure-python-wheel-for-a-package

I do not understand how micropip looks these things up
but I found this (which seems useful):

• https://micropip.pyodide.org/en/stable/project/usage.html
• and this also micropip.install(..., keep_going=True) to get a list of all packages with missing wheels.

and I came up with this:

import asyncio, micropip
asyncio.run(micropip.install(["sgp4==2.24"], keep_going=True))

I also tried this for skyfield and got same result:

asyncio.run(micropip.install(["skyfield"], keep_going=True))

Which confirms that sgp4 is the only package used in skyfield that it can't find a python 3 wheel for...

When I look under files on pypi I see CPYTHON for your wheels and Python 3 for pure packages.
Below, I am using Caeroc pure python package as a comparison because I know its a pure python package:
On Pypi under Files:

• For a purepython package (caeroc) I see:
  • caeroc-0.0.4a0-py3-none-any.whl
  • 46.0 kB [view details]
  • Uploaded Feb 14, 2025 [Python 3]
• Whereas for sgp4 I see "CPYTHON" rather than "PYTHON 3"
  • [sgp4-2.24-cp312-cp312-win_amd64.whl
  • `163.5 kB [view details]'
  • Uploaded Feb 16, 2025 [CPython 3.12] [Windows x86-64]

SO

How to make sure the build is a purepython wheel ?
Found these:

• https://discuss.python.org/t/easiest-way-to-determine-pure-python-sdists/58256/9

poss solution ?:

• Support building pure Python wheels pypa/cibuildwheel#1021

But I don't think I know enough to help further than this.
At least I hope its helpful.
Cheers...

[Neon22]

Additionally found this error message in cibuildwheel

If you intend to build a pure-Python wheel, you don't need cibuildwheel
Use:
 - `pip wheel .`,
 - `pipx run build --wheel`,
 - `uv build --wheel`, etc. instead.
  
 You only need cibuildwheel if you have compiled (not Python) code in your wheels making them depend on the platform.

[brandon-rhodes]

Hmmm. I am still getting the same error - even when forcing to 2.24 ("sgp4==2.24")

The new package that I linked to isn't called sgp4 but sgp4_pure_python, so you will need to try installing the package under that name. It might not make Skyfield happy yet, because, come to think of it, I probably failed to add a provides= field saying that it provides the sgp4 capability. But first let's test whether you can install sgp4_pure_python in your environment at all. If it does install successfully, and you can ask for a satellite position as shown in the sgp4 documentation, then we can declare the experiment a success, and I can re-release sgp4_pure_python with a proper provides= field. But let's see if it installs for you first.

[Neon22]

Gosh, so sorry I did not read that right :(
Yes its working perfectly:

• https://pyscript.com/@neon22/sgp4-starter-pkg/latest?files=main.py,pyscript_py.toml

And I checked skyfield as well, trying to load it after loading sgp4_pure_python and as you surmised it fails for same reasons.

[brandon-rhodes]

Yay! I'm glad the install worked. I have just released a quick follow-up version of sgp4_pure_python, this time with a field provides = that says it provides sgp4. So I think if you install sgp4_pure_python and then follow up with trying to install Skyfield, then the second install step will be satisfied that the requirement sgp4 is met, and won't try downloading and installing sgp4 itself? Try it out and let me know what happens.

[Neon22]

Alas the skyfield demo replies with:

File "/lib/python3.12/site-packages/micropip/install.py", line 57, in install
    raise ValueError(
        ValueError: Can't find a pure Python 3 wheel for: 'sgp4>=2.2'
        See: https://pyodide.org/en/stable/usage/faq.html#why-can-t-micropip-find-a-pure-python-wheel-for-a-package

I will ask on the pyscript forum if there is a way to force a specific package loading order.
But I suspect micropip can't work out that sgp4_pure_python meets the sgp4>=2.2 requirement

[brandon-rhodes]

Is there any equivalent in that environment to --no-deps, where it wouldn't even try doing its own work to figure out dependencies?

Or, is there any way you can provide the source code yourself? You could just grab the files from Skyfield, sgp4_pure_python, and jplephem, and place them in your project yourself, and skip the install step.

[Neon22]

Hmmm interesting quesion. I have asked on the pyscript discourse - waiting for an answer.

Yes - micropip does have a nodeps option await micropip.install("pkg", deps=False)
But not sure how to invoke it in the pyscript toml file.

Other possibility is to link to all the packages that skyfield depends on then
individually load the skyfield rawgithub files skyfield
(just as I did in the earlier sgp4 example: https://pyscript.com/@neon22/sgp4-starter-pkg/latest?files=pyscript_py.toml)

but that's about 40 files... so I'll wait for the pyscript response first :)

[Neon22]

OK. Alas not getting any traction from pyodide or pyscript side.
I will attempt to scrape all the files I need :(

[Neon22]

run into a bit of a showstopper.
I can't upload files like de421.bsp manually as they are too large.
I can't reach them directly because https: is not supported for the jpl URL - well that's what the error message says.

I think I have passed my technical knowledge threshold to solve these problems further.

Thanks for your efforts on my behalf.
I will keep an eye on developments

[Neon22]

pyscript now has fsspec which should get around the large file problems.
But I can't get past the packaging problems.

SO I will wait patiently for a pure python release of skyfield in the future.
Thanks heaps for your efforts Brandon. Cheers...