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[BUG] No module named 'dataclasses' under Python 3.6

See original GitHub issue

Describe the bug

Under FastAPI 0.49.0 and Python 3.6, a simple API throws an exception:

File "./app/__init__.py", line 1, in <module>
--
  | from fastapi import FastAPI
  | File "/opt/app-root/lib/python3.6/site-packages/fastapi/__init__.py", line 7, in <module>
  | from .applications import FastAPI
  | File "/opt/app-root/lib/python3.6/site-packages/fastapi/applications.py", line 3, in <module>
  | from fastapi import routing
  | File "/opt/app-root/lib/python3.6/site-packages/fastapi/routing.py", line 6, in <module>
  | from fastapi.dependencies.models import Dependant
  | File "/opt/app-root/lib/python3.6/site-packages/fastapi/dependencies/models.py", line 3, in <module>
  | from fastapi.security.base import SecurityBase
  | File "/opt/app-root/lib/python3.6/site-packages/fastapi/security/__init__.py", line 2, in <module>
  | from .http import (
  | File "/opt/app-root/lib/python3.6/site-packages/fastapi/security/http.py", line 5, in <module>
  | from fastapi.exceptions import HTTPException
  | File "/opt/app-root/lib/python3.6/site-packages/fastapi/exceptions.py", line 3, in <module>
  | from fastapi.utils import PYDANTIC_1
  | File "/opt/app-root/lib/python3.6/site-packages/fastapi/utils.py", line 2, in <module>
  | from dataclasses import is_dataclass
  | ModuleNotFoundError: No module named 'dataclasses'

To Reproduce

Create a simple API:

from fastapi import FastAPI

app = FastAPI(title='example', description='just a test', docs_url='/', redoc_url=None)

@app.get('/api/test')
async def index(foo: str = 'default', bar: str = None):
    return {
        'foo': foo,
        'bar': bar
    }

Attempt to run the API under Python 3.6 and observe the thrown exception

Expected behavior

The API should be available and not raise an exception. However, it does work under Python 3.7.

Environment

OS: Red Hat OpenShift, Python 3.6 container
FastAPI Version: 0.49.0
Python version: 3.6.3

Issue Analytics

State:
Created 4 years ago
Comments:7 (4 by maintainers)

Top GitHub Comments

1reaction

command-tabcommented, Feb 18, 2020

Ohhh, you know what, my local development environment is Python 3.7.x. I’ll bet that Pipfile.lock doesn’t include dataclasses because this environment didn’t need it, but my OpenShift production environment needs it because it’s 3.6. I bet if I were using a requirements.txt file instead of a full-graph lockfile, this wouldn’t be an issue.

0reactions

tiangolocommented, Apr 6, 2020

Thanks for the help here @dmontagu 🍰 🙇‍♂️

Thanks @command-tab for reporting back and closing the issue 👍