Wednesday, 16 September 2015

Python Facebook Data tutorial - Post to Facebook page in 4 steps

In this tutorial, you will learn how to post to a Facebook page's wall (acting as the page) using Python. It includes step by step instructions to create a new page, register an app with Facebook and some python code. 

I have a similar Python tutorial for Twitter.

Step 1

  • First, create a new Facebook page. Select appropriate page type, fill in description and other relevant fields.
  • On the new page, go to About tab, and note the Facebook Page ID.
  • We will post to this page's wall, acting as the page.

Step 2

  • Now create a Facebook App which will be used to access Facebook's Graph API.
  • Go to Facebook Apps dashboard -> Click Add a New App -> Choose platform WWW -> Choose a new name for your app -> Click Create New Facebook App ID -> Create a New App ID -> Choose Category (I chose "Entertainment") -> Click Create App ID again.
  • Go back to Apps dashboard -> Select the new app -> Settings -> Basic -> Enter Contact Email. This is required to take your app out of the sandbox.
  • Go to Status & Review -> Do you want to make this app and all its live features available to the general public? -> Toggle the button to Yes -> Make App Public? ->Yes. This will enable others to see posts by your app in their timelines - otherwise, only you will see the wall posts by the app. This took me some very frustating hours to figure out! These two stackoverflow posts were very helpful.
  • Now - you should see a green dot next to app's name, and the text This app is public and available to all users.
  • Make a note of the App ID and App Secret (Click Show next to it; you will be asked to re-enter your Facebook password).

Step 3

  • In this step we will obtain obtain Facebook OAuth token. A long-lived token at that! Read about Facebook access tokens. Some more helpful articles about Facebook token process.
  • Go to Graph API Explorer -> In the Application drop down -> Select the app created in Step 2 -> Click Get Access Token -> In Permissions popup go to Extended Permissionstab -> Select manage_pages, and publish_actions These permissions will allow your app to publish posts acting as the page -> Click Get Access Token -> You will see a message saying "{App} would like to post publicly to Facebook for you. Who do you want to share these posts with?" -> I chose Public for maximum visibility - as I wanted to post to a public page.
  • You might be asked to Turn On Platform if you disabled it previously, enable it! If you mess this step up, just go to your App Settings - remove the app and try again.
  • Make a note of the short-lived token shown in Graph API Explorer.
  • Facebook has deprecated offline access, the next best thing is long-lived token which expires in 60 days. We will convert the short-lived access token noted above to a long-lived token. This helped me figure it out.

For that, fill in the values in the URL below and open it in a browser:
https://graph.facebook.com/oauth/access_token?
  client_id={APP_ID}&
  client_secret={APP_SECRET}&
  grant_type=fb_exchange_token&
  fb_exchange_token={EXISTING_ACCESS_TOKEN}
  • You should see access_token={...}&expires={...}. This new access_token is the long-lived token we will use in our Python script.
  • long-lived token will also expire eventually, be prepared to perform this Step 3 again before that happens! If you do not want to deal with that just save the page_access_tokencomputed in Step 4 - and you can use it forever, as according to Facebook's documentationa page access token obtained from long-lived user token will not have any expiry time.

Step 4

  • We will use Facebook Python SDK to access Facebook's Graph API. You can install it using pip: pip install facebook-sdk (again, use of virtualenv is highly recommended).

Finally, this python script will post to Facebook page's wall:
import facebook

def main():
  # Fill in the values noted in previous steps here
  cfg = {
    "page_id"      : "VALUE",  # Step 1
    "access_token" : "VALUE"   # Step 3
  }

  api = get_api(cfg)
  msg = "Hello, Kalyan! have a nice day"
  status = api.put_wall_post(msg)

def get_api(cfg):
  graph = facebook.GraphAPI(cfg['access_token'])
  # Get page token to post as the page. You can skip 
  # the following if you want to post as yourself. 
  resp = graph.get_object('me/accounts')
  page_access_token = None
  for page in resp['data']:
    if page['id'] == cfg['page_id']:
      page_access_token = page['access_token']
  graph = facebook.GraphAPI(page_access_token)
  return graph
  # You can also skip the above if you get a page token:
  # http://stackoverflow.com/questions/8231877/facebook-access-token-for-pages
  # and make that long-lived token as in Step 3

if __name__ == "__main__":
  main()

Next steps
Allow multiple people to log-in to the app? I am not sure how to exactly do it, but here are a few pointers:
  • First step would be to add a login dialogue - instead of Step 3. This will be a popup from facebook.com which will show which permissions your app is requesting.
  • The 'login' API call will return a short-lived token. This is the tricky part, user is viewing a facebook.com page right now, how will your app get the auth token? Might be easier to do using their Javascript login flow. Other option is to give a redirect URL - which will be called when the popup is closed (and token added as a parameter).
  • Once you get the short-lived token, you can follow the tutorial - convert to long-livedand store that in a database - sqlite3 works very well for small prototypes.
  • Read these two links to understand more: Facebook.com - Manual login flow,Facebook.com Web login flow (javascript).
  • If required, renew the long-lived token for your users.
Post to your own wall or wall of a friend?
  • You can post to your own wall, read the first example here.
  • Posting to friend's wall has been deprecated, most probably due to SPAM :) Read here.


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