python-pptx-wasm

A WASM JavaScript library for manipulating PowerPoint presentations via python-pptx and Pyodide.

Features

• ✅ Read/write .pptx presentations with the full python-pptx API
• ✅ WebAssembly-powered via Pyodide
• ✅ Works in browser and Node.js
• ✅ Intelligent type inference

Install

1. Install dependencies:

$ npm install --save python-pptx-wasm pyodide

2. Download the latest recipes (packages.tar.gz) from python-pptx-recipe, and extract them into a fixed location, e.g.: project_root/assets/recipes

Usage

import fs from 'node:fs';
import { loadPyodide } from 'pyodide';
import { init, Presentation } from 'python-pptx-wasm';

const main = async () => {
  const pyodide = await loadPyodide({
    // Assuming recipes are extracted into `project_root/assets/recipes`
    lockFileURL: `project_root/assets/recipes/pyodide-lock.json`
  });

  await init(pyodide);

  const prs = Presentation();
  const slide1 = prs.slides.add_slide(prs.slide_layouts[0]);
  slide1.shapes.title!.text = 'Slide 1 Title';

  
  prs.save((buffer) => {
    // handle file buffer here
    fs.writeFileSync(`output_file.pptx`, buffer);
  });

  prs.end()
}

main()

Use with Bundler

If you are using a bundler in a web environment (e.g., Vite):

1. Download and extract recipes into public/recipes.

2. Install Vite plugin and update vite.config.ts:

$ npm install vite-plugin-static-copy @types/node --dev

// vite.config.ts
import { defineConfig } from "vite";
import { viteStaticCopy } from "vite-plugin-static-copy";
import { dirname, join } from "node:path";
import { fileURLToPath } from "node:url";

const PYODIDE_EXCLUDE = [
  "!**/*.{md,html}",
  "!**/*.d.ts",
  "!**/*.whl",
  "!**/node_modules",
];

export function viteStaticCopyPyodide() {
  const pyodideDir = dirname(fileURLToPath(import.meta.resolve("pyodide")));
  return viteStaticCopy({
    targets: [
      {
        src: [join(pyodideDir, "*")].concat(PYODIDE_EXCLUDE),
        dest: "assets",
      },
    ],
  });
}

export default defineConfig({
  plugins: [viteStaticCopyPyodide()],
  optimizeDeps: { exclude: ["pyodide"] }
});

3. Inside the codes:

import { loadPyodide } from 'pyodide';
import { init, Presentation } from 'python-pptx-wasm';

const main = async () => {
  const baseURL = window.location.origin + import.meta.env.BASE_URL

  // full url is required by pyodide
  const pyodide = await loadPyodide({
    indexURL: `${baseURL}assets`,
    // Assuming recipes are extracted into `public/recipes`
    lockFileURL: `${baseURL}recipes/pyodide-lock.json`
  });

  await init(pyodide);

  const prs = Presentation();
  const slide1 = prs.slides.add_slide(prs.slide_layouts[0]);
  slide1.shapes.title!.text = 'Slide 1 Title';

  // save file in browser
  prs.save((buffer) => {
    // buffer will be a Unit8array
    // @ts-ignore
    const blob = new Blob([buffer], { type: "application/vnd.openxmlformats-officedocument.presentationml.presentation" });
    const a = document.createElement("a");
    a.href = url;
    a.download = 'output_file.pptx';
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
    URL.revokeObjectURL(url);
  });

  prs.end()
}

main()

Technical Details

1. Differences from python-pptx

   python-pptx-wasm reimplements all core classes and method signatures of python-pptx in JavaScript, and calls the actual Python code via a Pyodide bridge.

   Note: The part components from python-pptx are not implemented.

2. The end() method

   Since python-pptx runs inside Pyodide, memory is not released automatically.

   When using python-pptx-wasm, you must manually call end() to free it:

   import { Presentation } from 'python-pptx-wasm';
   
   // Assuming already initialized
   const prs = Presentation();
   
   // ...
   // Perform operations on prs
   
   // Release memory
   prs.end()

3. File handling

   Unlike python-pptx, you cannot pass a file path directly.

   In python-pptx-wasm, all files are handled and passed as Uint8Array buffers:

   import fs from 'node:fs';
   import { Presentation } from 'python-pptx-wasm';
   
   // Assuming already initialized
   // Read a file as Uint8Array
   const prs = Presentation(new Uint8Array(fs.readFileSync(`existed_file.pptx`)));
   
   prs.end()

4. Length units

   python-pptx-wasm reimplements the length unit helpers from python-pptx:

   • Length
   • Centipoints
   • Cm
   • Emu
   • Inches
   • Mm
   • Pt

   Example:

   import { Presentation, Emu } from 'python-pptx-wasm';
   import { MSO_AUTO_SHAPE_TYPE } from 'python-pptx-wasm/pptx/enum';
   
   // Assuming already initialized
   const prs = Presentation();
   
   // Create a new slide
   const slide = prs.slides.add_slide(prs.slide_layouts[6]);
   
   // Add a shape using Emu for size/position
   slide.shapes.add_shape(MSO_AUTO_SHAPE_TYPE.RECTANGLE, Emu(914400), Emu(914400), Emu(1828800), Emu(914400));
   
   prs.end()

License

MIT License