Building from sources

If you are building the latest development version of Pyodide from the `main`
branch, please make sure to follow the build instructions from the dev
version of the documentation at
[pyodide.org/en/latest/](https://pyodide.org/en/latest/development/building-from-sources.html)

Pyodide can be built from sources on different platforms,

on Linux it is easiest using the Pyodide Docker image. This approach works with any native operating system as long as Docker is installed. You can also build on your native Linux OS if the correct build prerequisites are installed.
on MacOS it is recommended to install dependencies via conda-forge or using Homebrew, particularly with the M1 ARM CPU. Building with Docker is possible but very slow.
It is not possible to build on Windows, but you can use Windows Subsystem for Linux to create a Linux build environment.

Build instructions

Using Docker

We provide a Debian-based x86_64 Docker image (pyodide/pyodide-env) on Docker Hub with the dependencies already installed to make it easier to build Pyodide.

These Docker images are also available from the Github packages at
[`github.com/orgs/pyodide/packages`](https://github.com/orgs/pyodide/packages).

Install Docker
From a git checkout of Pyodide, run ./run_docker
Run make to build.

You can control the resources allocated to the build by setting the env
vars `EMSDK_NUM_CORE`, `EMCC_CORES` and `PYODIDE_JOBS` (the default for each is
4).

If running make deterministically stops at some point, increasing the maximum RAM usage available to the docker container might help. (The RAM available to the container is different from the physical RAM capacity of the machine.) Ideally, at least 3 GB of RAM should be available to the docker container to build Pyodide smoothly. These settings can be changed via Docker preferences (see here).

You can edit the files in the shared pyodide source folder on your host machine (outside of Docker), and then repeatedly run make inside the Docker environment to test your changes.

Using `make`

Make sure the prerequisites for emsdk are installed. Pyodide will build a custom, patched version of emsdk, so there is no need to build it yourself prior.

You need Python 3.11.2 to run the build scripts. To make sure that the correct Python is used during the build it is recommended to use a virtual environment or a conda environment.


```{tab-item} Linux

To build on Linux, you need:

- A working native compiler toolchain, enough to build
  [CPython](https://devguide.python.org/getting-started/setup-building/index.html#linux).
- CMake (required to install Emscripten)

```

```{tab-item} Linux with conda


You would need a working native compiler toolchain, enough to build
  [CPython](https://devguide.python.org/getting-started/setup-building/index.html#linux), for example,
- `apt install build-essential` on Debian based systems.
- Conda which can be installed from [MiniForge](https://github.com/conda-forge/miniforge)

Then install the required Python version and other build dependencies in a separate conda environment,

    conda env create -f environment.yml
    conda activate conda-forge

```
```{tab-item} MacOS with conda

You would need,
- System libraries in the root directory:
  `xcode-select --install`
- Conda which can be installed using [Miniforge](https://github.com/conda-forge/miniforge) (both for Intel and M1 CPU)


Then install the required Python version and other build dependencies in a separate conda environment,

    conda env create -f environment.yml
    conda activate conda-forge

```

```{tab-item} MacOS with Homebrew

To build on MacOS with Homebrew, you need:

- System command line tools
  `xcode-select --install`
- [Homebrew](https://brew.sh/) for installing dependencies
- `brew install coreutils cmake autoconf automaker libtool`
- It is also recommended installing the GNU patch and
  GNU sed (`brew install gpatch gnu-sed`)
  and [re-defining them temporarily as `patch` and
  `sed`](https://formulae.brew.sh/formula/gnu-sed).
```

If you encounter issues with the requirements, it is useful to check the exact
list in the
[Dockerfile](https://github.com/pyodide/pyodide/blob/main/Dockerfile) which is
tested in the CI.

You can install the Python dependencies from the requirement file at the root of Pyodide folder: pip install -r requirements.txt

After installing the build prerequisites, run from the command line:

make

(partial-builds)=

Partial builds

To build a subset of available packages in Pyodide, set the environment variable PYODIDE_PACKAGES to a comma separated list of packages. For instance,

PYODIDE_PACKAGES="toolz,attrs" make

Dependencies of the listed packages will be built automatically as well. The package names must match the folder names in packages/ exactly; in particular they are case-sensitive.

If PYODIDE_PACKAGES is not set, a minimal set of packages necessary to run the core test suite is installed, including "micropip", "pyparsing", "pytz", "packaging", "Jinja2", "regex". This is equivalent to setting PYODIDE_PACKAGES='tag:core' meta-package. Other supported meta-packages are,

"tag:min-scipy-stack": includes the "core" meta-package as well as some core packages from the scientific python stack and their dependencies: "numpy", "scipy", "pandas", "matplotlib", "scikit-learn", "joblib", "pytest". This option is non exhaustive and is mainly intended to make build faster while testing a diverse set of scientific packages.
"*" builds all packages
You can exclude a package by prefixing it with "!".

micropip and distutils are always automatically included.

Environment variables

The following environment variables additionally impact the build:

PYODIDE_JOBS: the -j option passed to the emmake make command when applicable for parallel compilation. Default: 3.
PYODIDE_BASE_URL: Base URL where Pyodide packages are deployed. It must end with a trailing /. Default: ./ to load Pyodide packages from the same base URL path as where pyodide.js is located. Example: {{PYODIDE_CDN_URL}}
EXTRA_CFLAGS : Add extra compilation flags.
EXTRA_LDFLAGS : Add extra linker flags.

Setting EXTRA_CFLAGS="-D DEBUG_F" provides detailed diagnostic information whenever error branches are taken inside the Pyodide core code. These error messages are frequently helpful even when the problem is a fatal configuration problem and Pyodide cannot even be initialized. These error branches occur also in correctly working code, but they are relatively uncommon so in practice the amount of noise generated isn't too large. The shorthand make debug automatically sets this flag.

In certain cases, setting EXTRA_LDFLAGS="-s ASSERTIONS=1 or ASSERTIONS=2 can also be helpful, but this slows down the linking and the runtime speed of Pyodide a lot and generates a large amount of noise in the console.

7.3 KiB Raw Blame History