SQLite objects created in a thread can only be used in that same thread

[Vosloo]

Problem description

Hello, I am trying to create a micro-service (with Flask) that use the library for getting synsets of a given word. I've noticed some unexpected behaviour when creating quering for synsets and Flask. For the attached code below I am getting an error:

ProgrammingError('SQLite objects created in a thread can only be used in that same thread.
The object was created in thread id 139815518537536 and this is thread id 139811777947392.

Code to reproduce

# foo.py
import wn
from wn.morphy import Morphy

class Foo:
    def __init__(self):
        self.wnde, self.morphy = self._initialize_wn()

    def _initialize_wn(self) -> tuple[wn.Wordnet, Morphy]:
        print("Initializing Wordnet...")
        wn.download("odenet")

        wnde = wn.Wordnet(lang="de")
        morphy = Morphy(wnde)
        wnde.lemmatizer = morphy

        return wnde, morphy

    def get_synsets(self, word: str) -> list:
        return self.wnde.synsets(word)

from flask import Flask
from foo import Foo

app = Flask(__name__)
foo = Foo()

@app.route("/", methods=["POST])
def do_stuff():
    word = request.form["data"]
    return {"data": foo.generate(word)}, 200

if __name__ == "__main__":
    app.run(
        threaded=True,  # Doesn't matter here if True or False, error still present
        host="0.0.0.0",
        debug=True,
    )

Expected behavior

We should get a list of synsets.

Environment

• Python 3.10.5
• Wn 0.9.3
• Lexicons:
  -- odenet 1.4 [de] Offenes Deutsches WordNet (only using this one)
  -- oewn 2021 [en] Open English WordNet

[goodmami]

@Vosloo thanks for the detailed report. SQLite doesn't allow multithreading by default. Have you tried using the wn.config.allow_multithreading option?

import wn
wn.config.allow_multithreading = True

Also see #86.

[goodmami]

I'm going to close this, but feel free to reopen if my suggestion above doesn't work. I tried it using your code to reproduce the issue (which BTW wasn't usable without a few fixes) and I got around the ProgrammingError, so I'll assume that this fixes the problem.

[Vosloo]

I wasn't aware of such an option and it does indeed work, thank You!