CODEWITHSUNDEEP
pythonclassimportsqliteflask
matt hoover
matt hoover

Reputation: 346

Trouble with class imports in flask application

I am trying to build a small web app for my analyst team. They just need a repository with which they can add and view the queries that they have written.

Thus far, I have been unable to implement my app because I can't import functions across the views/classes. Can someone help me figure out what my issue is?

I receive this error: 

File "C:\Users\Intern2\PycharmProjects\queries-Final2\queries_Final2.py", line 12, in <module>
from search_queries import SearchQueries
ImportError: cannot import name SearchQueries

I think that issue has to do with the fact that I try to import each file into the other file. However, I don't know of any other way to do this.

Here is my code:

queries_Final2.py (main application file)

from __future__ import with_statement
from sqlite3 import dbapi2 as sqlite3
from flask import Flask, request, session, g, redirect, url_for, abort,\
render_template, flash, _app_ctx_stack
import flask
import settings
import functools

# Views
from main import Main
from login import Login
from search_queries import SearchQueries
from add_queries import AddQueries
from edit_queries import EditQueries

DATABASE = 'C:\\Users\\Intern2\\PycharmProjects\\queries-Final2\\queriesDB.db'

app = flask.Flask(__name__)
app.config.from_object(__name__)
app.config.from_envvar('FLASKR_SETTINGS', silent=True)
app.secret_key = settings.secret_key

app.add_url_rule('/search-queries/',
view_func=SearchQueries.as_view('search-queries'),
methods=["GET", "POST"])

app.add_url_rule('/add-queries/',
view_func=AddQueries.as_view('add-queries'),
methods=["GET", "POST"])

def init_db():
"""Creates the database tables."""
with app.app_context():
    db = get_db()
    with app.open_resource('schema.sql') as f:
        db.cursor().executescript(f.read())
    db.commit()

def get_db():
"""Opens a new database connection if there is none yet for the
current application context.
"""
    top = _app_ctx_stack.top
    if not hasattr(top, 'sqlite_db'):
        top.sqlite_db = sqlite3.connect(app.config['DATABASE'])
    return top.sqlite_db

Display Queries view/class

from __future__ import with_statement
from sqlite3 import dbapi2 as sqlite3
 from flask import Flask, request, session, g, redirect, url_for, abort,\
render_template, flash, _app_ctx_stack
import flask
import settings
import functools
from queries_Final2 import get_db
import utils

class SearchQueries(flask.views.MethodView):
    @utils.login_required
def get(self):
    db = get_db()
    cur = db.execute('select title, columns, query, notes, tags from entries order by id desc')
    entries = [dict(title=row[0], columns=row[1], query=row[2],notes=row[3],tags=row[4]) for row in cur.fetchall()]
    return render_template('search-queries.html', entries=entries)

Add queries class/view

from __future__ import with_statement
from flask import Flask, request, session, g, redirect, url_for, abort,\
render_template, flash, _app_ctx_stack
import flask
import functools
import utils
from queries_Final2 import get_db

class AddQueries(flask.views.MethodView):
    @utils.login_required
def get(self):
    return flask.render_template('add-queries.html')

def post(self):
    db = get_db()
    db.execute('insert into entries (title, columns, query, notes, tags) values (?, ?, ?, ?, ?)',
    [request.form['title'],
     request.form['columns'],
     request.form['query'],
     request.form['notes'],
     request.form['tags']
    ])
    db.commit()
    flash('New entry was successfully posted')
    return flask.render_template('search-queries.html')

Any ideas would be greatly appreciated. Thanks in advance.

Upvotes: 2

Views: 2722

Answers (1)

orokusaki
orokusaki

Reputation: 57198

You have a circular import triggered by from queries_Final2 import get_db.

You're doing this, effectively (pseudo-code):

# Inside module A
import x from module B
    -> goes to module B to get x
    -> module B begins loading its imports (happens on first import)
    -> module B imports y from module A
    -> module B fails to import y from module A because module A is still being defined

Over time, you'll learn how to abstract your tools in a manner that will avoid this problem, but in the meantime, you can fix it by simply moving the lines from queries_Final2 import get_db to inside your get and post functions, instead of leaving them at the module level.

Upvotes: 3

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