Python Package and Methods not Importing

Question

I built a simple class with a couple methods to make my life a little easier when loading data into Postgres with Python. I also attempted to package it so I could pip install it (just to experiment, never done that before).

import psycopg2
from sqlalchemy import create_engine
import io


class py_psql:

    engine = None

    def engine(self, username, password, hostname, port, database):
        connection = 'postgresql+psycopg2://{}:{}@{}:{}/{}'.format(ntid.lower(), pw, hostname, port, database)
        self.engine = create_engine(connection)


    def query(self, query):
        pg_eng = self.engine
        return pd.read_sql_query(query, pg_eng)


    def write(self, write_name, df, if_exists='replace', index=False):
        mem_size = df.memory_usage().sum()/1024**2
        pg_eng = self.engine

        def write_data():
            df.head(0).to_sql(write_name, pg_eng, if_exists=if_exists,index=index)
            conn = pg_eng.raw_connection()
            cur = conn.cursor()
            output = io.StringIO()
            df.to_csv(output, sep='\t', header=False, index=False)
            output.seek(0)
            contents = output.getvalue()
            cur.copy_from(output, write_name, null="")
            conn.commit()

        if mem_size > 100:
            validate_size = input('DataFrame is {}mb, proceed anyway? (y/n): '.format(mem_size))
            if validate_size == 'y':        
                write_data()
            else:
                print("Canceling write to database")
        else:
            write_data()

My package directory looks like this:

py_psql
    py_psql.py
    __init__.py
setup.py

My init.py is empty since I read elsewhere that I was able to do that. I'm not remotely an expert here...

I was able to pip install that package and import it, and if I were to paste this class into a python shell, I would be able to do something like

test = py_psql()
test.engine(ntid, pw, hostname, port, database)

and have it create the sqlalchemy engine. However, when I import it after the pip install I can't even initialize a py_psql object:

>>> test = py_psql()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'module' object is not callable

>>> py_psql.engine(ntid, pw, hostname, port, database)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'py_psql' has no attribute 'engine'

I'm sure I'm messing up something obvious here, but I found the process of packaging fairly confusing while researching this. What am I doing incorrectly?

Answer 1

Are you sure you imported your package correctly after pip install?

For example:

from py_psql.py_psql import py_psql
test = py_psql()
test.engine(ntid, pw, hostname, port, database)