CODEWITHSUNDEEP
pythonpostgresqlamazon-ec2flask-sqlalchemy
Daniel Hair
Daniel Hair

Reputation: 270

SqlAlchemy query result outputting

I am trying to query one of my tables in my Postgres database using SqlAlchemy in Python 3. It runs the query fine but as I go through each row in the result that SqlAlchemy returns, I try to use the attribute 'text' (one of my column names). I receive this error:

'str' object has no attribute 'text'

I have printed the attribute like so:

for row in result:
   print(row.text)

This does not give the error. The code that produces the error is below. However, to give my environment:

I have two servers running. One is for my database the other is for my python server.

Database Server:

Server with Python

Files related:

import sqlalchemy as sa
from sqlalchemy.ext.automap import automap_base
from sqlalchemy.orm import Session
import re
from nltk import sent_tokenize

class DocumentProcess:
  def __init__(self):
    ...
    Engine = sa.create_engine(
        CONFIG.POSTGRES_URL,
        client_encoding='utf8',
        pool_size=20,
        max_overflow=0
    )

    # initialize SQLAlchemy
    Base = automap_base()

    # reflect the tables
    Base.prepare(Engine, reflect=True)

    # Define all needed tables
    self.Document = Base.classes.documents

    self.session = Session(Engine)
    ...

  def process_documents(self):
    try:
        offset = 5
        limit = 50
        ###### This is the query in question ##########
        result = self.session.query(self.Document) \
            .order_by(self.Document.id) \
            .offset(offset) \
            .limit(limit)
        for row in result:
          # The print statement below does print out the text
          print(row.text)
          # when passing document.text to sent_tokenize, it
          # gives the following error:
          # 'str' object has no attribute 'text'
          snippets = sent_tokenize(row.text.strip('\n')) # I have removed strip, but the same problem
    except Exception as e:
        logging.info(format(e))
        raise e

This is my model for Document, in my PostgreSQL database:

class Document(db.Model):
    __tablename__ = "documents"

    id = db.Column(db.Integer, primary_key=True)
    text = db.Column(db.Text)
    tweet = db.Column(db.JSON)
    keywords = db.Column(db.ARRAY(db.String), nullable=True)

    def to_dict(self):
        return dict(
            id=self.id,
            text=self.text,
            tweet=self.tweet,
            keywords=self.keywords
        )

    def json(self):
        return jsonify(self.to_dict())

    def __repr__(self):
        return "<%s %r>" % (self.__class__, self.to_dict())

Things I have tried

  1. Before, I did not have order_by in the Document query. This was working before. However, even removing order_by does not fix it anymore.

  2. Used a SELECT statement and went through the result manually, but still the same result

What I haven't tried

  1. I am wondering if its because I named the column 'text'. I noticed that when I write this query out in postgres, it highlights it as a reserved word. I'm confused why my query worked before, but now it doesn't work. Could this be the issue?

Any thoughts on this issue would be much appreciated.

Upvotes: 0

Views: 3333

Answers (2)

viralshah009
viralshah009

Reputation: 81

You are likely to get this error in PostgreSQL if you are creating a foreign table and one of the column datatype is text. Change it to character varying() and the error disappears!

Upvotes: 0

Daniel Hair
Daniel Hair

Reputation: 270

It turns out that text is a reserved word in PostgreSQL. I renamed the column name and refactored my code to match. This solved the issue.

Upvotes: 2

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