Error connecting to a DB in Python

Question

I’m having trouble connecting to a database by a script I developed in Python.

It’s probably some logic error involving the variables I couldn’t decipher and I wish someone could help me.

This is a piece of code...

def create(self, params, name_table):
    credentials = {
        "host": os.getenv("HOST"),
        "db_name": os.getenv("DB_NAME"),
        "user": os.getenv("USER"),
        "password": os.getenv("PASSWORD")
    }

    try:
        conn = psycopg2.connect(f"host={credentials['host']} "
                                f"dbname={credentials['db_name']} "
                                f"user={credentials['user']} "
                                f"password={credentials['password']}")

The environment variables (HOST, DB_NAME, USER, PASSWORD) are defined in my OS.