local postgresql environment doesn't connect with sqlalchemy

Question

I have a python code called list.py which is used so I can interact with local postgresql database named data_sample. This is my code:

import os
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker

engine = create_engine(os.getenv("data_sample"))
db = scoped_session(sessionmaker(bind=engine))

def main():
    flights = db.execute("SELECT origin, destination, duration FROM flights").fetchall()
    for flight in flights:
        print(f"{flight.origin} to {flight.destination}, {flight.duration} minutes.")

if __name__ == "__main__":
    main()

When I execute the code as python list.py, I get the following error:

Traceback (most recent call last):
  File "list.py", line 6, in <module>
    engine = create_engine(os.getenv("data_sample"))
  File "/Users/admin/.pyenv/versions/3.7.3/lib/python3.7/site-packages  /sqlalchemy/engine/__init__.py", line 500, in create_engine
    return strategy.create(*args, **kwargs)
  File "/Users/admin/.pyenv/versions/3.7.3/lib/python3.7/site-packages/sqlalchemy/engine/strategies.py", line 56, in create
    plugins = u._instantiate_plugins(kwargs)
AttributeError: 'NoneType' object has no attribute '_instantiate_plugins'

It seems like it doesn't know my database called data_sample. How do I fix this?

are you certain that the os.getenv() is correct? afaik it gets the value for the environment variable specified. — ewokx
– ewokx, Commented Jul 7, 2020 at 8:17
I see you've updated the code; but you didn't update the traceback, if it is the same error. — ewokx
– ewokx, Commented Jul 7, 2020 at 8:19
the traceback is still the same, i just edited it due to some typos I've made — Franz Zapanta
– Franz Zapanta, Commented Jul 7, 2020 at 8:28
but the traceback still shows your 'postgresl' code, which isn't in your code. — ewokx
– ewokx, Commented Jul 7, 2020 at 8:30

Atharva · Accepted Answer · 2020-07-07 10:48:44Z

0

Refer this link

os.getenv is used to get the value of environment variable

Use this instead:

engine = create_engine("postgresql://username:password@localhost:port/name_of_database")

If you haven't changed the default settings then your username will be postgres and port will be 5432.

answered Jul 7, 2020 at 10:48

Atharva

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