Unable to start a Session in Flask within a function - session

Question

I'm running Flask Session and using Eve as an API. For the Session code I'm following the example here https://pythonhosted.org/Flask-Session/
from flask import Flask, session
from flask.ext.session import Session
app = Flask(__name__)
# Check Configuration section for more details
SESSION_TYPE = 'redis'
app.config.from_object(__name__)
Session(app)
#app.route('/set/')
def set():
session['key'] = 'value'
return 'ok'
#app.route('/get/')
def get():
return session.get('key', 'not set')
I have an Eve API located under /api, and I want to avoid starting a new Session for those requests at least.
I want to start my flask Session only if the request.environ['PATH_INFO'] doesn't start with '/api/' but whenever I put Session() anywhere else it fails.
Following the example:
sess = Session()
sess.init_app(app)
When I try to do that in before_request or similar, then I get:
A setup function was called after the first request was handled.
and if I try to start a session in a normal content generator I get:
AttributeError: 'SecureCookieSession' object has no attribute 'sid'
How can I start a session conditionally, depending on the path/environment/etc?
My current code looks like this:
import flask
import xml.etree.ElementTree as ElementTree
from bson.objectid import ObjectId
from random import shuffle, choice as pick
from cgi import escape as escapehtml
from time import mktime
from urllib import quote as escapeurl, unquote_plus as unescapeurl
from flask import Flask, request, session, render_template, send_from_directory, jsonify, redirect, abort
from flask.ext.session import Session
from flask.ext.login import LoginManager, login_user, logout_user, current_user, UserMixin, user_logged_in, login_required, fresh_login_required
from itsdangerous import TimedJSONWebSignatureSerializer as Serializer, BadSignature, SignatureExpired, URLSafeTimedSerializer
from flask_mail import Mail, Message
from wtforms import Form, BooleanField, PasswordField
from flask.ext.mongoengine import MongoEngine
from flask.ext.security import Security, MongoEngineUserDatastore, RoleMixin, UserMixin
from flask.ext.principal import Principal, Permission, RoleNeed
from flask_security.forms import RegisterForm, Required, StringField
from flask_images import Images
from eve import Eve
from eve.auth import TokenAuth
from flask.ext.moment import Moment
from eve.io.mongo import Validator
from flask.ext.cors import CORS, cross_origin
from app.admin.one1 import one1
from app.emails.emails import emails
from app.alligator.alligator import alligator
from app.data.ndm_feed.ndm_feed import ndm_feed
from flask.ext import excel
...
login_serializer = URLSafeTimedSerializer(app.secret_key)
login_manager = LoginManager()
app.config.from_object(__name__)
login_manager.init_app(app)
Session(app)
and to avoid starting sessions for API calls I am trying to do things like this:
#app.before_request
def before_request():
if not request.environ['PATH_INFO'].startswith('/api/'):
Session(app)
or the equivalent:
#app.before_request
def before_request():
if not request.environ['PATH_INFO'].startswith('/api/'):
sess = Session()
sess.init_app(app)
But I can't seem to find a way to do it without the errors above.
How can I start a Flask session conditionally, depending on the path/environment/etc?

Answer 1

Actually your app already created before you use this: #app.before_request so it means you are late to add new configuration or extension initialize. Bu you can do with Blueprint:
# api.py
from flask import Blueprint
from flask_session import Session
sess = Session()
api = Blueprint('api', __name__)
# yourapp.py
...
def create_app():
...
try:
from api import api, sess
sess.init_app(app)
app.register_blueprint(api)
# views.py
#api.route('/set/')
def set():
session['key'] = 'value'
return 'ok