Azure web app AttributeError: module 'typing' has no attribute '_ClassVar'

Question

Hi, Im doing some tests with the Azure services. In this case Im trying to deploy a ML model, trained with the Azure ML service AutoML in a web app for inference. I have the following files in the project directory:

main.py

requirements.txt

model.pkl

startup.sh

The main.py script is really simple:

import pickle
import logging
import os
from fastapi import FastAPI, Request



app = FastAPI()
logging.basicConfig(level=logging.INFO,
                    format="%(asctime)s - %(levelname)s - %(name)s - %(message)s",
                    datefmt="%Y-%m-%d %H:%M:%S")
LOGGER = logging.getLogger(__name__)

def load_model():
    path = os.path.join(os.path.dirname(__file__), "model.pkl")    
    with open(path, 'rb') as f:
        model = pickle.load(f)
    return model

model = load_model()
TARGET_NAMES = ['No Failure', 'Failure']

@app.post("/predict_class")
async def predict_class(request: Request):
    req = await request.json()
    data = req["data"]
    y_pred = model.predict(data)[0]
    pred_class = TARGET_NAMES[y_pred]

    LOGGER.info(f"Request: {data} y_pred: {pred_class}")
    response = {"class": pred_class}
    return response

Im getting the following traceback error:

2024-05-21T23:31:35.516743913Z File "/tmp/8dc79afc5b4d09d/antenv/lib/python3.9/site-packages/dataclasses.py", line 800, in _process_class
2024-05-21T23:31:35.516951440Z cls_fields = [_get_field(cls, name, type)
2024-05-21T23:31:35.516961970Z File "/tmp/8dc79afc5b4d09d/antenv/lib/python3.9/site-packages/dataclasses.py", line 800, in 
2024-05-21T23:31:35.517165168Z cls_fields = [_get_field(cls, name, type)
2024-05-21T23:31:35.517175407Z File "/tmp/8dc79afc5b4d09d/antenv/lib/python3.9/site-packages/dataclasses.py", line 659, in _get_field
2024-05-21T23:31:35.517361835Z if (_is_classvar(a_type, typing)
2024-05-21T23:31:35.517372214Z File "/tmp/8dc79afc5b4d09d/antenv/lib/python3.9/site-packages/dataclasses.py", line 550, in _is_classvar
2024-05-21T23:31:35.517546770Z return type(a_type) is typing._ClassVar
2024-05-21T23:31:35.517556809Z AttributeError: module 'typing' has no attribute '_ClassVar'/home/LogFiles/2024_05_21_10-30-0-213_docker.log (https://test-poc-azure.scm.azurewebsites.net/api/vfs/LogFiles/2024_05_21_10-30-0-213_docker.log)

In the requirements.txt I have the following packages:

fastapi
scikit-learn
uvicorn
azureml
azureml-train
azureml-core
azureml-sdk
azureml-train-core
azureml-train-automl-runtime

I tried using python 3.8, 3.9, 3.10, 3.11 and 3.12. All the python versions available in web apps.

I have tried every workaround found on google also, none of those worked.

Any idea how can this be solved?

Answer

Thanks for posting your question in the Microsoft Q&A forum.

It seems like Azure has a problematic import path, thus wrong typing package is imported. Python 3.8 has the typing package built-in, but it's trying to use the obsolete one installed with pip, which is causing the problem.

Add this at the very beginning of your file, before any imports:

import

It essentially prioritizes built-in packages instead of ones installed with pip.

https://stackoverflow.com/questions/75473492/attributeerror-module-typing-has-no-attribute-classvar-azure-function

** Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful **

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Azure web app AttributeError: module 'typing' has no attribute '_ClassVar'

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