WASM IN PYTHON

2 min readApr 13, 2022

Building python code with WASM

Today we’ll learn how to build python code with WebAssembly using wasmtime.

DOCKER INSTALLATION :

1. Uninstall old versions to avoid errors:

$ sudo apt-get remove docker docker-engine docker.io containerd runc

2. Install using the repository:

$ sudo apt-get update

$ sudo apt-get install \
    ca-certificates \
    curl \
    gnupg \
    lsb-release

3. Add Docker’s official GPG key and setup stable repository:

$ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
$ echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu \
$(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

4. Install Docker Engine:

$ sudo apt-get update
$ sudo apt-get install docker-ce docker-ce-cli containerd.io
$ sudo apt-get install docker-ce=5:20.10.14~3-0~ubuntu-focal docker-ce-cli=5:20.10.14~3-0~ubuntu-focal containerd.io

5. Verify that Docker Engine is installed by the command:

$ sudo docker run hello-world

CPython’s WASM build:

Clone the repo:

git clone https://github.com/singlestore-labs/python-wasi/

2. Go to the directory ‘python-wasi’ :

cd python-wasi

3. Build the docker image using this command:

docker build -f docker/Dockerfile -t wasi-build:latest docker

4. Let’s start the docker container and mount the current and working directory inside the docker container by the command:

docker run -it --rm -v $(pwd):$(pwd) -w $(pwd) wasi-build:latest bash

5. To download the CPython source, dependencies and to build the CPython’s WASM build, run:

./run.sh

Wasmtime

Wasmtime is a small and efficient runtime for WebAssembly & WASI.

$ curl https://wasmtime.dev/install.sh -sSf | bash
$ wasienv install-sdk unstable

Running the python code on wasmtime

Create a file named CounDigit.py and write the Program:

def countDigit(n):
 count = 0
 while n != 0:
  n //= 10
  count += 1
 return countn = 345289467
print("Number of digits : % d" % (countDigit(n)))

Run the program

1. Switch to the root python-wasi directory.

2. Run the python code in wasmtime using the command:

wasmtime run — mapdir=$(pwd)/opt::opt \
 — opt/wasi-python/bin/python3.wasm -c “$(cat $(pwd)/fib.py)”

Output:

Number of digits :9

Hope it helps! Do let me know in the comments!