Convert SQL query to CSV file in Python

def sql_query_to_csv(query_output, columns_to_exclude=""):
 """ Converts output from a SQLAlchemy query to a .csv string.

 Parameters:
  query_output (list of <class 'SQLAlchemy.Model'>): output from an SQLAlchemy query.
  columns_to_exclude (list of str): names of columns to exclude from .csv output.

 Returns:
  csv (str): query_output represented in .csv format.

 Example usage:
  users = db.Users.query.filter_by(user_id=123)
  csv = sql_query_to_csv(users, ["id", "age", "address"]
 """
 rows = query_output
 columns_to_exclude = set(columns_to_exclude)

 #create list of column names
 column_names = [i for i in rows[0].__dict__]
 for column_name in columns_to_exclude:
  column_names.pop(column_names.index(column_name))

 #add column titles to csv
 column_names.sort()
 csv = ", ".join(column_names) + "\n"

 #add rows of data to csv
 for row in rows:
  for column_name in column_names:
   if column_name not in columns_to_exclude:
    data = str(row.__dict__[column_name])
    #Escape (") symbol by preceeding with another (")
    data.replace('"','""')
    #Enclose each datum in double quotes so commas within are not treated as separators
    csv += '"' + data + '"' + ","
  csv += "\n"

 return csv

from datetime import datetime

from sqlalchemy import create_engine
from sqlalchemy import Column, String, Integer, DateTime
from sqlalchemy.orm import sessionmaker
from sqlalchemy.exc import SQLAlchemyError
from sqlalchemy.ext.declarative import declarative_base

from sql_query_to_csv import sql_query_to_csv

Base = declarative_base()

# define model
class User(Base):
    __tablename__ = 'User'
    id       = Column(Integer, primary_key=True)
    name     = Column(String, nullable=False)
    fullname = Column(String, nullable=False)
    birth    = Column(DateTime)

engine = create_engine('sqlite:///db.sqlite')
Base.metadata.create_all(bind=engine)

users = [
    User(name='JH',
         fullname='Jimi Hendrix',
         birth=datetime(1942,11,27)),
    User(name='RJ',
         fullname='Robert Johnson',
         birth=datetime(1943,12,8)),
    User(name='JM',
         fullname='Jim Morrison',
         birth=datetime(1911,5,8))]

# create session
Session = sessionmaker()
Session.configure(bind=engine)
session = Session()

# add data
session.add_all(users)
session.commit()

# query database
query = session.query(User).all()

# output all users to csv
csv_1 = sql_query_to_csv(query)
print(csv_1)

# output all users to csv, excluding some columns
csv_2 = sql_query_to_csv(query, ["birth", "id", "_sa_instance_state"])
print(csv_2)