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Merged
merged 2 commits into from
Nov 19, 2025
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feat: configure cpython source #183

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7fc120f
feat: configure cpython source
Sl1mb0 Nov 18, 2025
c3aa651
docs: add section for configuring cpython source
Sl1mb0 Nov 19, 2025
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9 changes: 7 additions & 2 deletions guests/python/Justfile
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,11 @@ SHA256_WASI_SDK_SYSROOT := "35172f7d2799485b15a46b1d87f50a585d915ec662080f005d99

PYTHON_VERSION_FULL := PYTHON_VERSION_MAJOR + "." + PYTHON_VERSION_MINOR + "." + PYTHON_VERSION_MICRO

# Configurable URLs for Python SDK downloads (with defaults)
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Copilot AI Nov 18, 2025

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The new environment variables PYTHON_SDK_BASE_URL, PYTHON_SDK_URL, and BUILD_PYTHON_SDK_URL should be documented so users know they can configure custom download locations. Consider adding a section to guests/python/README.md under the "Build" section or to CONTRIBUTING.md explaining these configuration options and their use cases (e.g., using custom mirrors, air-gapped environments).

Suggested change
# Configurable URLs for Python SDK downloads (with defaults)
# Python SDK download URL configuration
#
# The following environment variables can be set to customize the download locations for the Python WASM SDK:
# - PYTHON_SDK_BASE_URL: Base URL for Python SDK releases (default: official GitHub release)
# - PYTHON_SDK_URL: Full URL for the pre-built Python SDK zip file
# - BUILD_PYTHON_SDK_URL: Full URL for the build Python SDK zip file
#
# These variables are useful for:
# - Using custom mirrors or internal artifact repositories
# - Building in air-gapped or restricted network environments
# - Overriding the default download source for testing or reliability
#
# Example usage:
# export PYTHON_SDK_BASE_URL="https://my-mirror.local/python-wasi"
# just build-release
#

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@Sl1mb0 Sl1mb0 Nov 19, 2025

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Thanks copilot!

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@crepererum crepererum Nov 19, 2025

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I personally feel this is sufficiently described in the README as well, so the doc here seems a bit redundant. But I leave that up to you.

PYTHON_SDK_BASE_URL := env_var_or_default("PYTHON_SDK_BASE_URL", "https://github.com/brettcannon/cpython-wasi-build/releases/download")
PYTHON_SDK_URL := env_var_or_default("PYTHON_SDK_URL", PYTHON_SDK_BASE_URL + "/v" + PYTHON_VERSION_FULL + "/python-" + PYTHON_VERSION_FULL + "-wasi_sdk-" + WASI_SDK_VERSION_MAJOR + ".zip")
BUILD_PYTHON_SDK_URL := env_var_or_default("BUILD_PYTHON_SDK_URL", PYTHON_SDK_BASE_URL + "/v" + PYTHON_VERSION_FULL + "/_build-python-" + PYTHON_VERSION_FULL + "-wasi_sdk-" + WASI_SDK_VERSION_MAJOR + ".zip")

DOWNLOADS_DIR := source_directory() / "downloads"

export PYO3_CROSS_PYTHON_VERSION := PYTHON_VERSION_MAJOR + "." + PYTHON_VERSION_MINOR
Expand Down Expand Up @@ -49,7 +54,7 @@ download-python-sdk:
--tlsv1.2 \
--location \
--output "python-sdk.zip" \
"https://github.com/brettcannon/cpython-wasi-build/releases/download/v{{PYTHON_VERSION_FULL}}/python-{{PYTHON_VERSION_FULL}}-wasi_sdk-{{WASI_SDK_VERSION_MAJOR}}.zip"
"{{PYTHON_SDK_URL}}"

curl \
--fail \
Expand All @@ -59,7 +64,7 @@ download-python-sdk:
--tlsv1.2 \
--location \
--output "build-python-sdk.zip" \
"https://github.com/brettcannon/cpython-wasi-build/releases/download/v{{PYTHON_VERSION_FULL}}/_build-python-{{PYTHON_VERSION_FULL}}-wasi_sdk-{{WASI_SDK_VERSION_MAJOR}}.zip"
"{{BUILD_PYTHON_SDK_URL}}"

echo "{{SHA256_PYTHON_SDK}} python-sdk.zip" | sha256sum -c
echo "{{SHA256_PYTHON_SDK_BUILD}} build-python-sdk.zip" | sha256sum -c
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29 changes: 29 additions & 0 deletions guests/python/README.md
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Expand Up @@ -16,6 +16,35 @@ just build-release
## Python Version
We currently bundle [Python 3.14.0], [build for WASI](https://docs.python.org/3/library/intro.html#webassembly-platforms).

## Custom CPython Configuration
You can configure the build to use a custom CPython source by setting the following environment variables:

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@crepererum crepererum Nov 19, 2025

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This could mention PYTHON_SDK_BASE_URL too, which is useful esp. when you fork https://github.com/brettcannon/cpython-wasi-build since it will "just work" (i.e. the two sub-URLs are correctly derived for your fork as well).


- `PYTHON_SDK_BASE_URL`: Base URL to download the Python WASI SDK artifacts. This
should point to a location containing both the main SDK archive and the build
artifacts archive.
- `PYTHON_SDK_URL`: URL to download the main Python WASI SDK archive. This
should point to an artifact containing the pre-built Python runtime and
standard library for WASI. Will override `PYTHON_SDK_BASE_URL` if set.
- `BUILD_PYTHON_SDK_URL`: URL to download the build artifacts archive. This
should point to an artifact containing the compiled Python libraries (like
`libpython3.14.a`, `libmpdec.a`, etc.) needed for static linking. Will override
`PYTHON_SDK_BASE_URL` if set.

If these environment variables are not set, the build will use the default URLs pointing to the official [CPython WASI build releases](https://github.com/brettcannon/cpython-wasi-build/releases).

Example usage:
```console
export PYTHON_SDK_URL="https://example.com/custom-python-sdk.zip"
export BUILD_PYTHON_SDK_URL="https://example.com/custom-build-python-sdk.zip"
just build-debug

# Or

export PYTHON_SDK_BASE_URL="https://example.com/custom-python-sdk-base/"
just build-debug
```

## Python Standard Library
In contrast to a normal Python installation there are a few notable public[^public] modules **missing** from the [Python Standard Library]:

Expand Down