Unable to set line 4 to input

I’m trying to make a Raspberry Pi 3 REST API that provides temperature and humidity with DHT22. The whole code:

from flask import Flask, jsonify, request
from sds011 import SDS011
from adafruit_dht import DHT22
import board
import os
import time

app = Flask(__name__)
dht = DHT22(board.D4)

def get_dht_data():
    while True:
        try:
            temperature, humidity = dht.temperature, dht.humidity
            print(temperature, humidity)
            if temperature is not None and humidity is not None:
                return temperature, humidity
            else:
                raise
        except:
            time.sleep(0.5)

@app.route('/', methods=['GET'])
def status():
    temperature, humidity = get_dht_data()

    return jsonify({
        'temperature': temperature,
        'humidity': humidity
    })

if __name__ == '__main__':
    app.run(debug=True)

However, when I start server, it shows message

Unable to set line 4 to input

and temperature and humidity is always None. If I don’t run flask app but just DHT code, it works.

[monkeywire]

…it seems to work fine when I first boot up the raspberry pi and I can run the test code once and it works… After that if I try to run to the test code a second time I get the same error…

[Saeven]

Not even using Flask - just this script, is enough to make the RPI4 hang:

import time
import board
import adafruit_dht

dhtDevice = adafruit_dht.DHT22(board.D4)