h4l/v8serialize

Read & write JavaScript values from Python with the V8 serialization format.

Imagine having postMessage() between JavaScript and Python.

pip install v8serialize

Documentation

---

v8serialize

A Python library to read & write JavaScript values in V8 serialization format with Python.

Examples

These examples demonstrate serializing and deserializing the same selection of JavaScript values in Python and JavaScript. JavaScript types supported by JavaScript's structuredClone() algorithm can be serialized.

Serialize with Python

from base64 import b64encode
from datetime import datetime, UTC
import re

from v8serialize import dumps
from v8serialize.jstypes import JSObject, JSArray, JSUndefined

serialized = dumps(
    [
        "strings 🧵🧶🪡",
        123,
        None,
        JSUndefined,
        JSArray({0: 'a', 1: 'b', 123456789: 'sparse'}),
        JSObject({"msg": "Hi"}),
        b"\xc0\xff\xee",
        2**128,
        {"maps": True},
        {"sets", "yes"},
        re.compile(r"^\w+$"),
        datetime(2024, 1, 1, tzinfo=UTC),
    ]
)

print(b64encode(serialized).decode())

Output

/w9BDFMUc3RyaW5ncyDwn6e18J+ntvCfqqFVezBfYZaa7zpVAFMBYVUBUwFiVZWa7zpTBnNwYXJzZUADlprvOm9TA21zZ1MCSGl7AUIDwP/uWiIAAAAAAAAAAAAAAAAAAAAAATtTBG1hcHNUOgInUwRzZXRzUwN5ZXMsAlJTBV5cdyskgAJEAABAHyXMeEIkAAw=

Deserialize with Python

from base64 import b64decode
from v8serialize import loads

# The output of the JavaScript example
serialized = b64decode(
    "/w9BDGMccwB0AHIAaQBuAGcAcwAgAD7Y9d0+2PbdPtih3kn2ATBfYZaa7zpJACIBYUkCIgFiSaq03nUiBnNwYXJzZUADlprvOm8iA21zZyICSGl7AUIDwP/uWjAAAAAAAAAAAAAAAAAAAAAAAQAAAAAAAAA7IgRtYXBzVDoCJyIDeWVzIgRzZXRzLAJSIgVeXHcrJIACRAAAQB8lzHhCJAAM"
)
print(loads(serialized))

Output

JSArray([
  'strings 🧵🧶🪡',
  123,
  None,
  JSUndefined,
  JSArray({
    0: 'a',
    1: 'b',
    123456789: 'sparse',
  }),
  JSObject(msg='Hi'),
  JSArrayBuffer(b'\xc0\xff\xee'),
  340282366920938463463374607431768211456,
  JSMap({
    'maps': True,
  }),
  JSSet([
    'yes',
    'sets',
  ]),
  JSRegExp(source='^\\w+$', flags=<JSRegExpFlag.UnicodeSets: 256>),
  datetime.datetime(2024, 1, 1, 0, 0),
])

Serialize with Node.js / Deno

import * as v8 from "node:v8";

const sparseArray = ["a", "b"];
sparseArray[123456789] = "sparse";

const buffer = v8.serialize([
  "strings 🧵🧶🪡",
  123,
  null,
  undefined,
  sparseArray,
  { msg: "Hi" },
  Uint8Array.from([0xc0, 0xff, 0xee]).buffer,
  2n ** 128n,
  new Map([["maps", true]]),
  new Set(["yes", "sets"]),
  /^\w+$/v,
  new Date(Date.UTC(2024, 0, 1)),
]);

console.log(buffer.toString("base64"));

Output

/w9BDGMccwB0AHIAaQBuAGcAcwAgAD7Y9d0+2PbdPtih3kn2ATBfYZaa7zpJACIBYUkCIgFiSaq03nUiBnNwYXJzZUADlprvOm8iA21zZyICSGl7AUIDwP/uWjAAAAAAAAAAAAAAAAAAAAAAAQAAAAAAAAA7IgRtYXBzVDoCJyIDeWVzIgRzZXRzLAJSIgVeXHcrJIACRAAAQB8lzHhCJAAM

Deserialize with Node.js / Deno

import * as v8 from "node:v8";

// The output of the Python example
const buffer = Buffer.from(
  "/w9BDFMUc3RyaW5ncyDwn6e18J+ntvCfqqFVezBfYZaa7zpVAFMBYVUBUwFiVZWa7zpTBnNwYXJzZUADlprvOm9TA21zZ1MCSGl7AUIDwP/uWiIAAAAAAAAAAAAAAAAAAAAAATtTBG1hcHNUOgInUwN5ZXNTBHNldHMsAlJTBV5cdyskgAJEAABAHyXMeEIkAAw=",
  "base64"
);
console.log(v8.deserialize(buffer));

Output

[
  'strings 🧵🧶🪡',
  123,
  null,
  undefined,
  [ 'a', 'b', <123456787 empty items>, 'sparse' ],
  { msg: 'Hi' },
  ArrayBuffer { [Uint8Contents]: <c0 ff ee>, byteLength: 3 },
  340282366920938463463374607431768211456n,
  Map(1) { 'maps' => true },
  Set(2) { 'yes', 'sets' },
  /^\w+$/v,
  2024-01-01T00:00:00.000Z
]