Virtual file system support¶

The Pyodide kernel mounts a virtual /drive directory which allows access to files that are provided by JupyterLite.

{warning}
**NOTE:** The virtual file system **does not work when in private mode under Firefox** and you'll get permission errors. It will also fail to work if you **hard refresh** the page.

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from pathlib import Path

The kernel will be start in a location in the virtual drive.

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Path.cwd()

Directories¶

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a_dir = Path("dir")
a_dir.exists()

New paths should appear almost immediately in the file tree.

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a_dir.mkdir(exist_ok=True)

List directory content¶

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sorted(Path.cwd().glob("*"))

Remove¶

Contents should disappear immediately from the file browser when removed.

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a_dir.exists() and a_dir.rmdir()

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sorted(Path.cwd().glob("*"))

Reading/writing file¶

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txt = Path("test.txt")
txt.write_text("Hello! I write this from the kernel worker")

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txt.read_text()

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from PIL import Image

img = Path("pil_color.png")
Image.new("RGB", (60, 30), color=(73, 109, 137)).save(img)

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from IPython.display import Image, Markdown, display

Image(data=img, format="png")

Rename¶

Files can be renamed.

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txt.exists()

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txt.rename("test_rename.txt")

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txt.exists()

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sorted(Path.cwd().glob("*"))

Stat¶

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for path in sorted(Path.cwd().glob("*")):
    display(Markdown(f"- [{path}]({path.name})" "\n" f"  - `{path.stat()}`"))

Complex IO¶

Some libraries don't fully work as expected yet, such as sqlite3.

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import sqlite3

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def create_movies(path):
    path.unlink(missing_ok=True)
    con = sqlite3.connect(path)
    cur = con.cursor()
    with con:
        cur.execute("CREATE TABLE movie(title, year, score)")
        cur.execute(
            """
            INSERT INTO movie VALUES
                ('Monty Python and the Holy Grail', 1975, 8.2),
                ('And Now for Something Completely Different', 1971, 7.5)
            """
        )
    con.close()

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def query_movies(path):
    con = sqlite3.connect(path)
    cur = con.cursor()
    res = cur.execute("SELECT * FROM movie").fetchall()
    con.close()
    return res

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db = Path("tutorial.db")
try:
    create_movies(db)
    assert False, "if we got here, something awesome happened!"
except sqlite3.DatabaseError as err:
    print(err)

For now, one can work in a separate folder:

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tmp_db = Path("/tmp/tutorial.db")
create_movies(tmp_db)
display(*query_movies(tmp_db))

And copy (not rename) the file back out, and then reading works fine.

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import shutil

db.unlink(missing_ok=True)
shutil.copy2(tmp_db, db)
display(*query_movies(db))

By extension, SQLite databases hosted from the server will also be readable with sqlite3, such as the classic northwind example.

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con = sqlite3.connect("data/northwind.sqlite3")
cur = con.cursor()
display(*cur.execute("SELECT LastName, FirstName FROM Employees").fetchall())

Or even with pandas:

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import base64

import IPython
import pandas

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df = pandas.read_sql_query("SELECT * from Employees", con, "EmployeeID")
df["Photo"] = df["Photo"].apply(
    lambda raw: f"""<img src="data:image/png;base64,{base64.b64encode(raw).decode("utf-8")}"/>"""
)
IPython.display.HTML(df.T.to_html(escape=False))

{note}
Future work could potentially expose reasonably-sized queries against _huge_ databases
with techniques like [`sql.js-httpvfs`](https://github.com/phiresky/sql.js-httpvfs): see [the original post](https://phiresky.github.io/blog/2021/hosting-sqlite-databases-on-github-pages).