Following FastAPI Tutorial - Poetry install failing on Greenlet

Question

I'm currently attempting to learn to use FastAPI using the tutorial found here: https://christophergs.com/tutorials/ultimate-fastapi-tutorial-pt-7-sqlalchemy-database-setup/

Each step comes with it's own folder of items to work with and upon reaching "Part 7 - Database Setup with SQLAlchemy and Alembic" I've run into an issue where the poetry install continuously fails. The list dependencies are as follows:

[tool.poetry]
name = "app"
version = "0.0.1"
description = "Ultimate FastAPI Tutorial"
authors = ["ChristopherGS"]

[tool.poetry.dependencies]
python = "^3.8"
uvicorn = "~0.11.3"
fastapi = "~0.68.0"
python-multipart = "~0.0.5"
pydantic = {extras = ["email"], version = "~1.8.1"}
Jinja2 = "^3.0.1"
SQLAlchemy = "^1.4.22"
alembic = "^1.6.5"
tenacity = "^8.0.1"
greenlet = "^1.1.2"

However, each time it reaches the greenlet installation, it errors out at:

Package operations: 17 installs, 0 updates, 0 removals

  • Installing greenlet (1.1.2): Failed

  ChefBuildError

  Backend subprocess exited when trying to invoke build_wheel


# a million syntax errors


  at ~\AppData\Local\Programs\Python\Python311\Lib\site-packages\poetry\installation\chef.py:164 in _prepare
      160│
      161│                 error = ChefBuildError("\n\n".join(message_parts))
      162│
      163│             if error is not None:
    → 164│                 raise error from None
      165│
      166│             return path
      167│
      168│     def _prepare_sdist(self, archive: Path, destination: Path | None = None) -> Path:

Note: This error originates from the build backend, and is likely not a problem with poetry but with greenlet (1.1.2) not supporting PEP 517 builds. You can verify this by running 'pip wheel --no-cache-dir --use-pep517 "greenlet (==1.1.2)"'.

Is there a known solution for this problem? Not the most familiar with python and pip installing packages individually does not seem to be doing anything for me here.

Attempted to install packages individually with pip and also attempted to try upgrading the greenlet version, but that seems to be the latest version so nothing there either.

Answer 1

Before anything else, I'd try removing greenlet from the pyproject.toml as it's already a dependency of SQLAlchemy iirc and just let SQLAlchemy install it.

I had the same issue when greenlet 3.0.0 was released and I discovered two options which alternatively worked.

1. Recreate the poetry environment. Enter environment with poetry shell, then do poetry env info. Copy the Path to the env and do rm -rf <Path>. Finally do poetry install to recreate the environment with hopes that greenlet installs fine.
2. Manually install greenlet to a specific version that worked and lock that version in the pyproject.toml dependencies (not ideal).