Open Event API Server: Implementing FAQ Types

In the Open Event Server, there was a long standing request of the users to enable the event organisers to create a FAQ section.

The API of the FAQ section was implemented subsequently. The FAQ API allowed the user to specify the following request schema

 "data": {
   "type": "faq",
   "relationships": {
     "event": {
       "data": {
         "type": "event",
         "id": "1"
   "attributes": {
     "question": "Sample Question",
     "answer": "Sample Answer"


But, what if the user wanted to group certain questions under a specific category. There was no solution in the FAQ API for that. So a new API, FAQ-Types was created.

Why make a separate API for it?

Another question that arose while designing the FAQ-Types API was whether it was necessary to add a separate API for it or not. Consider that a type attribute was simply added to the FAQ API itself. It would mean the client would have to specify the type of the FAQ record every time a new record is being created for the same. This would mean trusting that the user will always enter the same spelling for questions falling under the same type. The user cannot be trusted on this front. Thus the separate API made sure that the types remain controlled and multiple entries for the same type are not there.

Helps in handling large number of records:

Another concern was what if there were a large number of FAQ records under the same FAQ-Type. Entering the type for each of those questions would be cumbersome for the user. The FAQ-Type would also overcome this problem

Following is the request schema for the FAQ-Types API

 "data": {
   "attributes": {
     "name": "abc"
   "type": "faq-type",
   "relationships": {
     "event": {
       "data": {
         "id": "1",
         "type": "event"



  • FAQ to FAQ-type is a many to one relation.
  • A single FAQ can only belong to one Type
  • The FAQ-type relationship will be optional, if the user wants different sections, he/she can add it ,if not, it’s the user’s choice.

Related links

Implementing Permissions for Orders API in Open Event API Server

Open Event API Server Orders API is one of the core APIs. The permissions in Orders API are robust and secure enough to ensure no leak on payment and ticketing.The permission manager provides the permissions framework to implement the permissions and proper access controls based on the dev handbook.

The following table is the permissions in the developer handbook.


List View Create Update Delete
Event organizer [1] [1] [1] [1][2] [1][3]
Registered user [4]
Everyone else
  1. Only self-owned events
  2. Can only change order status
  3. A refund will also be initiated if paid ticket
  4. Only if order placed by self

Super Admins and admins are allowed to create any order with any amount but any coupon they apply is not consumed on creating order. They can update almost every field of the order and can provide any custom status to the order. Permissions are applied with the help of Permission Manager which takes care the authorization roles. For example, if a permission is set based on admin access then it is automatically set for super admin as well i.e., to the people with higher rank.

Self-owned events

This allows the event admins, Organizer and Co-Organizer to manage the orders of the event they own. This allows then to view all orders and create orders with or without discount coupon with any custom price and update status of orders. Event admins can provide specific status while others cannot

if not has_access('is_coorganizer', event_id=data['event']):
   data['status'] = 'pending'

And Listing requires Co-Organizer access

elif not has_access('is_coorganizer', event_id=kwargs['event_id']):
   raise ForbiddenException({'source': ''}, "Co-Organizer Access Required")

Can only change order status

The organizer cannot change the order fields except the status of the order. Only Server Admin and Super Admins are allowed to update any field of the order.

if not has_access('is_admin'):
   for element in data:
       if element != 'status':
           setattr(data, element, getattr(order, element))

And Delete access is prohibited to event admins thus only Server admins can delete orders by providing a cancelling note which will be provided to the Attendee/Buyer.

def before_delete_object(self, order, view_kwargs):
   if not has_access('is_coorganizer',
       raise ForbiddenException({'source': ''}, 'Access Forbidden')

Registered User

A registered user can create order with basic details like the attendees’ records and payment method with fields like country and city. They are not allowed to provide any custom status to the order they are creating. All orders will be set by default to “pending”

Also, they are not allowed to update any field in their order. Any status update will be done internally thus maintaining the security of Order System. Although they are allowed to view their place orders. This is done by comparing their logged in user id with the user id of the purchaser.

if not has_access('is_coorganizer_or_user_itself', event_id=order.event_id, user_id=order.user_id):
   return ForbiddenException({'source': ''}, 'Access Forbidden')

Event Admins

The event admins have one more restriction, as an event admin, you cannot provide discount coupon and even if you do it will be ignored.

# Apply discount only if the user is not event admin
if data.get('discount') and not has_access('is_coorganizer', event_id=data['event']):

Also an event admin any amount you will provide on creating order will be final and there will be no further calculation of the amount will take place

if not has_access('is_coorganizer', event_id=data['event']):

Creating Attendees Records

Before sending a request to Orders API it is required to create to attendees mapped to some ticket and for this registered users are allowed to create the attendees without adding a relationship of the order. The mapping with the order is done internally by Orders API and its helpers.


  1. Dev Handbook – Niranjan R
    The Open Event Developer Handbook
  2. Flask-REST-JSONAPI Docs
    Permissions and Data layer | Flask-REST-JSONAPI
  3. A guide to use permission manager in API Server


Generating Ticket PDFs in Open Event API Server

In the ordering system of Open Event API Server, there is a requirement to send email notifications to the attendees. These attendees receive the URL of the pdf of the generated ticket. On creating the order, first the pdfs are generated and stored in the preferred storage location and then these are sent to the users through the email.

Generating PDF is a simple process, using xhtml2pdf we can generate PDFs from the html. The generated pdf is then passed to storage helpers to store it in the desired location and pdf-url is updated in the attendees record.

Sample PDF

PDF Template

The templates are written in HTML which is then converted using the module xhtml2pdf.
To store the templates a new directory was created at  app/templates where all HTML files are stored. Now, The template directory needs to be updated at flask initializing app so that template engine can pick the templates from there. So in app/ we updated flask initialization with

template_dir = os.path.dirname(__file__) + "/templates"

app = Flask(__name__, static_folder=static_dir, template_folder=template_dir)

This allows the template engine to pick the templates files from this template directory.

Generating PDFs

Generating PDF is done by rendering the html template first. This html content is then parsed into the pdf

file = open(dest, "wb")

pisa.CreatePDF(cStringIO.StringIO(pdf_data.encode('utf-8')), file)


The generated pdf is stored in the temporary location and then passed to storage helper to upload it.

uploaded_file = UploadedFile(dest, filename)

upload_path = UPLOAD_PATHS['pdf']['ticket_attendee'].format(identifier=get_file_name())

new_file = upload(uploaded_file, upload_path)

This generated pdf path is returned here

Rendering HTML and storing PDF

for holder in order.ticket_holders:

  if !=

      pdf = create_save_pdf(render_template('/pdf/ticket_attendee.html', order=order, holder=holder))


      pdf = create_save_pdf(render_template('/pdf/ticket_purchaser.html', order=order))

  holder.pdf_url = pdf


The html is rendered using flask template engine and passed to create_save_pdf and link is updated on the attendee record.

Sending PDF on email

These pdfs are sent as a link to the email after creating the order. Thus a ticket is sent to each attendee and a summarized order details with attendees to the purchased.






  html= MAILS[TICKET_PURCHASED_ATTENDEE]['message'].format(





  1. Readme – xhtml2pdf
  2. Using xhtml2pdf and create pdfs


Discount Codes in Open Event Server

The Open Event System allows usage of discount codes with tickets and events. This blogpost describes what types of discount codes are present and what endpoints can be used to fetch and update details.

In Open Event API Server, each event can have two types of discount codes. One is ‘event’ discount code, while the other is ‘ticket’ discount code. As the name suggests, the event discount code is an event level discount code and the ticket discount code is ticket level.

Now each event can have only one ‘event’ discount code and is accessible only to the server admin. The Open Event server admin can create, view and update the ‘event’ discount code for an event. The event discount code followsDiscountCodeEvent Schema. This schema is inherited from the parent class DiscountCodeSchemaPublic. To save the unique discount code associated with an event, the event model’s discount_code_id field is used.

The ‘ticket’ discount is accessible by the event organizer and co-organizer. Each event can have any number of ‘ticket’ discount codes. This follows the DiscountCodeTicket schema, which is also inherited from the same base class ofDiscountCodeSchemaPublic. The use of the schema is decided based on the value of the field ‘used_for’ which can have the value either ‘events’ or ‘tickets’. Both the schemas have different relationships with events and marketer respectively.

We have the following endpoints for Discount Code events and tickets:

The first endpoint is based on the DiscountCodeDetail class. It returns the detail of one discount code which in this case is the event discount code associated with the event.

The second endpoint is based on the DiscountCodeList class which returns a list of discount codes associated with an event. Note that this list also includes the ‘event’ discount code, apart from all the ticket discount codes.

class DiscountCodeFactory(factory.alchemy.SQLAlchemyModelFactory):
   class Meta:
       model = DiscountCode
       sqlalchemy_session = db.session
event_id = None
user = factory.RelatedFactory(UserFactory)
user_id = 1

Since each discount code belongs to an event(either directly or through the ticket), the factory for this has event as related factory, but to check for 
/events/<int:event_id>/discount-code endpoint we first need the event and then pass the discount code id to be 1 for dredd to check this. Hence, event is not included as a related factory, but added as a different object every time a discount code object is to be used.

@hooks.before("Discount Codes > Get Discount Code Detail of an Event > Get Discount Code Detail of an Event")
def event_discount_code_get_detail(transaction):
   GET /events/1/discount-code
   :param transaction:
   with stash['app'].app_context():
       discount_code = DiscountCodeFactory()
       event = EventFactoryBasic(discount_code_id=1)

The other tests and extended documentation can be found 


User Guide for the PSLab Remote-Access Framework

The remote-lab framework of the pocket science lab has been designed to enable user to access their devices remotely via the internet. The pslab-remote repository includes an API server built with Python-Flask and a webapp that uses EmberJS. This post is a guide for users who wish to test the framework. A series of blog posts have been previously written which have explored and elaborated various aspect of the remote-lab such as designing the API server, remote execution of function strings, automatic deployment on various domains etc. In this post, we shall explore how to execute function strings, execute example scripts, and write a script ourselves.

A live demo is hosted at . The API server is hosted at, and an API reference which is being developed can be accessed at . A screencast of the remote lab is also available

Create an account

Signing up at this point is very straightforward, and does not include any third party verification tools since the framework is under active development, and cannot be claimed to be ready for release yet.

Click on the sign-up button, and provide a username, email, and password. The e-mail will be used as the login-id, and needs to be unique.

Login to the remote lab

Use the email-id used for signing up, enter the password, and the app will redirect you to your new home-page, where you will be greeted with a similar screen.

Your home-page

On the home-page, you will find that the first section includes a text box for entering a function string, and an execute button. Here, you can enter any valid PSLab function such as `get_resistance()` , and click on the execute button in order to run the function on the PSLab device connected to the API server, and view the results. A detailed blog post on this process can be found here.

Since this is a new account, no saved scripts are present in the Your Scripts section. We will come to that shortly, but for now, there are some pre-written example scripts that will let you test them as well as view their source code in order to copy into your own collection, and modify them.

Click on the play icon next to `` in order to run the script. The eye icon to the right of the row enables you to view the source code, but this can also be done while the app is running. The multimeter app looks something like this, and you can click on the various buttons to try them out.

You may also click on the Source Code tab in order to view the source

Create and execute a small python script

We can now try to create a simple script of our own. Click on the `New Python Script` button in the top-bar to navigate to a page that will allow you to create and save your own scripts. We shall write a small 3-line code to print some sinusoidal coordinates, save it, and test it. Copy the following code for a sine wave with 30 points, and publish your script.

import numpy as np
print (x, np.sin(x))

Create a button widget and associate a callback to the get_voltage function

A small degree of object oriented capabilities have also been added, and the pslab-remote allows you to create button widgets and associate their targets with other widgets and labels.
The multimeter demo script uses this feature, and a single line of code suffices to demonstrate this feature.

button('Voltage on CH1 >',"get_voltage('CH1')","display_number")

You can copy the above line into a new script in order to try it out.

Associate a button’s callback to the capture routines, and set the target as a plot

The callback target for a button can be set to point to a plot. This is useful if the callback involves arrays such as those returned by the capture routines.

Example code to show a sine wave in a plot, and make button which will replace it with captured data from the oscilloscope:

import numpy as np
plt = plot(x, np.sin(x))
button('capture 1',"capture1('CH1',100,10)","update-plot",target=plt)
Figure: Demo animation from the plot_test example. Capture1 is connected to the plot shown.

Open Event Server: Getting The Identity From The Expired JWT Token In Flask-JWT

The Open Event Server uses JWT based authentication, where JWT stands for JSON Web Token. JSON Web Tokens are an open industry standard RFC 7519 method for representing claims securely between two parties. [source:]

Flask-JWT is being used for the JWT-based authentication in the project. Flask-JWT makes it easy to use JWT based authentication in flask, while on its core it still used PyJWT.

To get the identity when a JWT token is present in the request’s Authentication header , the current_identity proxy of Flask-JWT can be used as follows:

def example():
   return '%s' % current_identity


Note that it will only be set in the context of function decorated by jwt_required(). The problem with the current_identity proxy when using jwt_required is that the token has to be active, the identity of an expired token cannot be fetched by this function.

So why not write a function on our own to do the same. A JWT token is divided into three segments. JSON Web Tokens consist of three parts separated by dots (.), which are:

  • Header
  • Payload
  • Signature

The first step would be to get the payload, that can be done as follows:

token_second_segment = _default_request_handler().split('.')[1]


The payload obtained above would still be in form of JSON, it can be converted into a dict as follows:

payload = json.loads(token_second_segment.decode('base64'))


The identity can now be found in the payload as payload[‘identity’]. We can get the actual user from the paylaod as follows:

def jwt_identity(payload):
   Jwt helper function
   :param payload:
   return User.query.get(payload['identity'])


Our final function will now be something like:

def get_identity():
   To be used only if identity for expired tokens is required, otherwise use current_identity from flask_jwt
   token_second_segment = _default_request_handler().split('.')[1]
   missing_padding = len(token_second_segment) % 4
   payload = json.loads(token_second_segment.decode('base64'))
   user = jwt_identity(payload)
   return user


But after using this function for sometime, you will notice that for certain tokens, the system will raise an error saying that the JWT token is missing padding. The JWT payload is base64 encoded, and it requires the payload string to be a multiple of four. If the string is not a multiple of four, the remaining spaces can pe padded with extra =(equal to) signs. And since Python 2.7’s .decode doesn’t do that by default, we can accomplish that as follows:

missing_padding = len(token_second_segment) % 4

# ensures the string is correctly padded to be a multiple of 4
if missing_padding != 0:
   token_second_segment += b'=' * (4 - missing_padding)


Related links:

Stripe Authorization In Open Event API Server

The Open Event System supports payments through stripe. Stripe is a suite of APIs that powers commerce for businesses of all sizes. This blogpost covers testing of Stripe Authorization Schema and endpoints in the API Server.

The Stripe Authorization class provides the following endpoints:


In the pull request made for adding documentation and tests, these two endpoints were removed:


This is because each event can have only one stripe authorization, so there can not exist a list of stripe authorization objects related to an event.

The ‘stripe_authorization_list’ endpoint is made POST only. This is because Open Event does not allow individual resources’ list to be accessible. Since, there is no endpoint which returns a list of Stripe Authorizations the StripeAuthorizationList(ResourceListis removed.

The ResourceDetail class was modified to add a query to support  results from ‘/events/<int:event_id>/stripe-authorization’ endpoint suThe view_kwargs for the detail endpoint has to contain the resource id, so event_id from view_kwags is used to get the id for stripe authorization.

stripe_authorization = self.session.query(StripeAuthorization).filter_by(event_id=view_kwargs['event_id']).one()
view_kwargs['id'] =

Writing Test for Documentation

(Tests for the /events/1/stripe-authorization  is described here, for others please refer to links in additional references.)

To test the  /events/1/stripe-authorization endpoint for GET, we first insert a Stripe Authorization object into the database which will then be retrieved by the GET request and then compared with the expected response body from the documentation file.

Since stripe-auth has a required relationship with event class, an event must also exist for strie auth object to be created. The event is also required because the endpoint ‘events/’ expects an event object to exist. The StripeAuthorizationFactory takes care of this with event as a RelatedFactory. So when a StripeAuthorization object is inserted, an event is created first and passed as the required relationship to stripe_list_post endpoint.

The event is related to the stripe object by setting event_id = 1 in the factory.

Adding the pre-test hook for GET:

@hooks.before("StripeAuthorization > Stripe Authorization for an Event > Get Stripe Authorization Details of an Event")
def event_stripe_authorization_get_detail(transaction):
   GET /events/1/stripe-authorization
   :param transaction:
   with stash['app'].app_context():
       stripe = StripeAuthorizationFactory()

The expected response for this request can be found

Additional References:

Creating an Elementary Oscilloscope in PSLab’s Remote Framework

The last couple of blog posts explained how we could put together the versatility of ember components, the visual appeal of jqplot, the flexibility of Python Flask, and the simplicity of Python itself in order to make simple scripts for PSLab that would could be run on a server by a remote client anywhere on the web. We have also seen how callbacks could be assigned to widgets created in these scripts in order to make object oriented applications. In this blog post, we shall see how to assign a capture method to a button, and update a plot with the received data. It will also demonstrate how to use ember-lodash to perform array manipulations.

Specifying the return data type in the callback success routine

For a more instructive write-up on assigning callbacks, please refer to these posts .

Whenever the callback assigned to a button is a function that returns an array of elements, and the target for the resultant data is a plot, the stacking order of the returned array must be specified in order to change its shape to suit the plotting library. The default return data from a capture routine (oscilloscope) is made up of separate arrays for X coordinate and Y coordinate values. Since JQplot requires [X,Y] pairs , we must specify a stacking order of ‘xy’ so that the application knows that it must convert them to pairs (using lodash/zip)  before passing the result to the plot widget. Similarly, different stacking orders for capture2, and capture4 must also be defined.

Creating an action that performs necessary array manipulations and plots the received data

It can be seen from the excerpt below, that if the onSuccess target for a callback is specified to be a plot in the actionDefinition object, then the stacking order is checked, and the returned data is modified accordingly

Relevant excerpt from controllers/user-home.js/runButtonAction

if (actionDefinition.success.type === 'update-plot') {
  if (actionDefinition.success.stacking === 'xy') {
    $.jqplot(, [zip(...resultValue)]).replot();
  } else if (actionDefinition.success.stacking === 'xyy') {
    $.jqplot(, [zip(...[resultValue[0], resultValue[1]]), zip(...[resultValue[0], resultValue[2]])]).replot();
  } else if (actionDefinition.success.stacking === 'xyyyy') {
    $.jqplot(, [zip(...[resultValue[0], resultValue[1]]), zip(...[resultValue[0], resultValue[2]]), zip(...[resultValue[0], resultValue[3]]), zip(...[resultValue[0], resultValue[4]])]).replot();
  } else {
    $.jqplot(, resultValue).replot();


With the above framework in place, we can add a plot with the line plt = plot(x, np.sin(x)) , and associate a button with a capture routine that will update its contents with a single line of code: button(‘capture1’,”capture1(‘CH1’,100,10)”,”update-plot”,target=plt)

Final Result

The following script created on the pslab-remote platform makes three buttons and plots, and sets the buttons to invoke capture1, capture2, and capture4 respectively when clicked.

import numpy as np
plt = plot(x, np.sin(x))
button('capture 1',"capture1('CH1',100,10)","update-plot",target=plt)

plt2 = plot(x, np.sin(x))
button('capture 2',"capture2(50,10)","update-plot",target=plt2,stacking='xyy')

plt3 = plot(x, np.sin(x))
button('capture 4',"capture4(50,10)","update-plot",target=plt3,stacking='xyyyy')















Copying Event in Open Event API Server

The Event Copy feature of Open Event API Server provides the ability to create a xerox copy of event copies with just one API call. This feature creates the complete copy of event by copying the related objects as well like tracks, sponsors, micro-locations, etc. This API is based on the simple method where an object is first removed is from current DB session and then applied make_transient. Next step is to remove the unique identifying columns like “id”, “identifier” and generating the new identifier and saving the new record. The process seems simple but becomes a little complex when you have to generate copies of media files associated and copies of related multiple objects ensuring no orders, attendees, access_codes relations are copied.

Initial Step

The first thing to copy the event is first to get the event object and all related objects first

if view_kwargs.get('identifier').isdigit():
   identifier = 'id'

event = safe_query(db, Event, identifier, view_kwargs['identifier'], 'event_'+identifier)

Next thing is to get all related objects to this event.

Creating the new event

After removing the current event object from “db.session”, It is required to remove “id” attribute and regenerate “identifier” of the event.

db.session.expunge(event)  # expunge the object from session
delattr(event, 'id')
event.identifier = get_new_event_identifier()

Updating related object with new event

The new event created has new “id” and “identifier”. This new “id” is added into foreign keys columns of the related object thus providing a relationship with the new event created.

for ticket in tickets:
   ticket_id =
   db.session.expunge(ticket)  # expunge the object from session
   ticket.event_id =
   delattr(ticket, 'id')

Finishing up

The last step of Updating related objects is repeated for all related objects to create the copy. Thus a new event is created with all related objects copied with the single endpoint.


How to clone a sqlalchemy object

Reset password in Open Event API Server

The addition of reset password API in the Open Event API Server enables the user to send a forgot password request to the server so that user can reset the password. Reset Password API is a two step process. The first endpoint allows you to request a token to reset the password and this token is sent to the user via email. The second process is making a PATCH request with the token and new password to set the new password on user’s account.

Creating a Reset token

This endpoint is not JSON spec based API. A reset token is simply a hash of random bits which is stored in a specific column of user’s table.

hash_ = random.getrandbits(128)
self.reset_password = str(hash_)

Once the user completed the resetting of the password using the specific token, the old token is flushed and the new token is generated. These tokens are all one time use only.

Requesting a Token

A token can be requested on a specific endpoint  POST /v1/auth/reset-password
The token with the direct link will be sent to registered email.

link = make_frontend_url('/reset-password', {'token': user.reset_password})
send_email_with_action(user, PASSWORD_RESET,     
                       app_name=get_settings()['app_name'], link=link)

Flow with frontend

The flow is broken into 2 steps with front end is serving to the backend. The user when click on forget password will be redirected to reset password page in the front end which will call the API endpoint in the backend with an email to send the token. The email received will contain the link for the front end URL which when clicked will redirect the user to the front end page of providing the new password. The new password entered with the token will be sent to API server by the front end and reset password will complete.

Updating Password

Once clicked on the link in the email, the user will be asked to provide the new password. This password will be sent to the endpoint PATCH /v1/auth/reset-password. The body will receive the token and the new password to update. The user will be identified using the token and password is updated for the respective user.

   user = User.query.filter_by(reset_password=token).one()
except NoResultFound:
   return abort(
       make_response(jsonify(error="User not found"), 404)
   user.password = password


  1. Understand Self-service reset password
  2. Python – getrandbits()