pydantic.run

Python browser sandbox based on Pyodide. Write and share Python code, run it in the browser.

Built to demonstrate Pydantic, PydanticAI, and Pydantic Logfire.

If you choose to save code, it's stored in CloudFlare's R2 object storage, and should be available for one year.

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Dependencies

Dependencies are installed when code is run.

Dependencies can be defined in one of two ways:

Inferred from imports

If there's no metadata, dependencies are inferred from imports in the code.

import pydantic

class Model(pydantic.BaseModel):
    x: int

print(Model(x='42'))

Inline script metadata

As introduced in PEP 723, explained here, and popularised by uv — dependencies can be defined in a comment at the top of the file.

This allows use of dependencies that aren't imported in the code, and is more explicit.

# /// script
# dependencies = ["pydantic", "email-validator"]
# ///
import pydantic

class Model(pydantic.BaseModel):
    email: pydantic.EmailStr

print(Model(email='hello@pydantic.dev'))

It also allows version to be pinned for non-binary packages (Pyodide only supports a single version for the binary packages it supports, like pydantic and numpy).

# /// script
# dependencies = ["rich<13"]
# ///
import rich
from importlib.metadata import version

rich.print(f'[red]Rich version:[/red] [blue]{version('rich')}[/blue]')

Sandbox via link

To programmatically create a sandbox, make a GET request to https://pydantic.run/new, with the files parameter set to a JSON object containing the files you want to show.

The response is a 302 redirect to the newly created sandbox, hence you can direct a user to a sandbox with the code you want them to see. Repeated requests with the same files will use the same sandbox.

files should be an array of objects with the following keys:

• name - (string) the name of the file
• content - (string) the content of the file
• Optionally activeIndex - (integer) indicating which file/tab is open by default, the highest value wins

You can also set the tab parameter to select which tab is open by default, that advantage of using this over activeIndex is that it will reuse the same sandbox for requests choosing different tabs.

Here's a minimal HTML page that provides a link to create a new sandbox with two files:

<div>loading...</div>
<script>
  const files = [
    {
      name: 'main.py',
      content: 'print("This is an example!")',
      activeIndex: 1,
    },
    {
      name: 'another.py',
      content: 'x = 42\nprint(f"The answer is {x}")',
    },
  ]
  const redirectUrl = new URL('https://pydantic.run/new')
  redirectUrl.searchParams.append('files', JSON.stringify(files))
  document.querySelector('div').innerHTML = `<a href="${redirectUrl}">Click here to create a new sandbox</a>`
</script>

Demo here.