Publishing in Facebook each post from this blog

Some time ago we published the way for Extracting links from a webpage with Python as a first step for publishing complete blog posts in Facebook. The idea was to prepare the text obtained from an RSS feed in order to publish it in a Facebook page (or in other places). Let us remember that Facebook does not allow (or I didn’t find the way) to include html in the pages’ posts.
We had presented previously in Publishing in Twitter when posting here some related ideas, in that case for Twitter.

Now we are going to use the Facebook API and an unofficial package which implements it in Python, Facebook Python SDK.

We can install it with

fernand0@aqui:~$ sudo pip install facebook-sdk

It will need `BeautifulSoup` and `requests` (and maybe some other modules). If they are not installed in our system, we will get the adequate ‘complaints’. We can install them as usual with pip (or our preferred system).

We need some credentials in order to publish in Facebook. First we have to register our application in Facebook My Apps (button ‘Add a new App’ (there are plenty of tutorials if you need help). We will use the ‘advanced setup’ (registering web applications seems to be easier) and some identifiers will be provided (mainly the OAUTH token; we can find them at Myapps, following the link for our app). We will store this token in ~/.rssFacebook, and it will be later used in our program.
This configuration file is similar to this one


The program is very simple, it can be downloaded from (link to the version commented here, there have been some further evolutions).

The program starts reading the configuration about the available blogs and we need to choose one. If there were just one no selection would be needed:

config = ConfigParser.ConfigParser()[os.path.expanduser('~/.rssBlogs')])

print "Configured blogs:"

for section in config.sections():
        print str(i), ')', section, config.get(section, "rssFeed")
        i = i + 1

if (int(i)>1):
        i = raw_input ('Select one: ')
        i = 1

print "You have chosen ", config.get("Blog"+str(i), "rssFeed")

The configuration file must contain a section for each blog; each one of them will have an RSS feed, the Twitter account and the name of the Facebook page. For this site it would have the following entries:


Notice that the Facebook account is empty: this blog has not a Facebook page (yet?).
We could have a second blog:


This configuration file can have yet another field, linksToAvoid that will be used for selecting some links that won’t be shown (I have other blog and in this way I can avoid the categories’ links).

if (config.has_option("Blog"+str(i), "linksToAvoid")):
        linksToAvoid = config.get("Blog"+str(i), "linksToAvoid")
        linksToAvoid = ""

We will read now the last post of the blog and we will extract the text and links in a similar way as seen in Extracting links from a webpage with Python (not shown here).

And now the links we want to avoid:

                print linksToAvoid
                print re.escape(linksToAvoid)
                print str(link['href'])
                print, link['href'])
                if ((linksToAvoid =="")
                        or (not, link['href']))):
                        link.append(" ["+str(j)+"]")
                        linksTxt = linksTxt + "["+str(j)+"] " + link.contents[0] + "\n"
                        linksTxt = linksTxt + "    " + link['href'] + "\n"
                        j =  j + 1

We then check if the post contains some image. If not, we will not add an image, but Facebook will (it will be the first image that it can find in our page).
We could configure one that would be used in case of need (in case we have not included an image in our post and we do not like the one chosen by Facebook) or we can try to add always to our posts some image.

if len(pageImage) > 0:
        imageLink = (pageImage[0]["src"])
        imageLine = ""

Now we will read the Facebook configuration and we will ask for the list of pages the user manages (remember that we have established the desired one in ~/.rssBlogs):[os.path.expanduser('~/.rssFacebook')])
oauth_access_token= config.get("Facebook", "oauth_access_token")

graph = facebook.GraphAPI(oauth_access_token)
pages = graph.get_connections("me", "accounts")

We could define more Facebook accounts but I have not tested this feature, so maybe it won’t work as expected (and, of course, there is no way to select one of them).

for i in range(len(pages['data'])):
        if (pages['data'][i]['name'] == pageFB):
                print "Writing in... ", pages['data'][i]['name']
                graph2 = facebook.GraphAPI(pages['data'][i]['access_token'])
                        "feed", message = theSummary, link=theLink,
                        picture = imageLink,
                        name=theTitle, caption='',

statusTxt = "Publicado: "+theTitle+" "+theLink

This program has been tested during the last months and the solution seems to be working (maybe you’ll want to check the latest version that will have some bugs corrected).
The most cumbersome part was to get the credentials and register the app (with a ‘fake’ production step; for me it is ‘fake’ because I’m the only user of the app).

This post was published originally (in Spanish) at: Publicar en Facebook las entradas de este sitio.

If you have doubts, comments, ideas… Please comment!


Firing a camera when somebody is around

After the summer break we are returning with a small project. We added movement to our camera (Adding movement: servos) and with this we were able to change the orientation of the camera in the room (A mobile camera) but we weren’t able to see interesting things most of the time (it is difficult to find the adequate moments).

I was curious about proximity sensors, so I decided to give them a try buying a couple of HC-SR04, which work with ultrasounds.

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Ojos que no ven

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The objective is to take a picture when somebody/something is passing in front of the camera: for this we are measuring the distance to the obstacle in front of the sensor and when a change is observed we can suppose that there is something there.

I did some experiments with the Raspi but the results were unsatisfactory: measures are not accurate (it is easy to filter out the bad ones) and this is not adequate for our purposes.

Just in case, you can check an example in HC-SR04 Ultrasonic Range Sensor on the Raspberry Pi.

The connections:

The problems seem to be related to the fact that the raspi is not very good at real time and minor variations in time measurement can appear (with these sensors we are measuring the time that some sound pulses take to go and return until they find some obstacle).

Since we had an Arduino we decided to check if it was more adequate. This would allow us:

– More accurate measures.
– Learning the way to communicate the Raspberry Pi and the Arduino.

Of course, this will open the door for new experiments.

The connections with the Arduino:

Following HC-SR04 Ultrasonic Sensor it has been quite easy to prepare the Arduino sketch and to connect the sensor (the code is available at sketch.ino in its current format, there can be some changes in the future).

We found that the measures were more accurate: sometimes there can be a difference of one or two centimeters, but this is not a problem when we are trying to detect something passing because in this case there should be a difference of 20cms or more.

Now we needed a way to communicate the Arduino with the Raspberry (in order to reuse some previous code).

Arduino sends text that can be easily read and processed at the Raspberry.
There seem to be several ways to do the communication: a serial port over USB (Connect Raspberry Pi and Arduino with Serial USB Cable), using I2C (Raspberry Pi and Arduino Connected Using I2C) and by means of GPIO (Raspberry Pi and Arduino Connected Over Serial GPIO).
I chose the first one but I should experiment with the others in the near future.


while 1:
	distAnt = dist
	dist = int(ser.readline().strip().strip())

if abs(distAnt-dist)>10:
	print "Alert!!"

That is: we are storing the previous measurement (distAnt), we obtain a new one (dist = … ) and we activate an alert if there is a difference greater than 10 cms.

Since we wanted to take a picture, we have reused some code that can be seen at: A camera for my Raspberry Pi and, following previous ideas, we’ll send it by email (Sending an image by mail in Python).

The code can be seen at

There was a problem: we are establishing directly the connection with the mail server in order to send the image. We cannot avoid the time consumed by the camera (which is not negligible); but we can avoid waiting for the mail sending.
For this we are creating a subprocess (see multiprocessing) which does this part of the work.

p = Process(target=mail, args=(name,who))

That is, we take the picture and then we are launching a new process that will perform the sending. Since I had no previous experience with parallel coding in Python I’m not sure if some process cleaning/ending is needed. No sychronization nor waiting for the process to finish is needed, so all seems to be working well.

Some final remarks: none of these processes is really fast; nobody should expect to use this code as a ‘trap’ for taking pictures of a flying bird (even a child running won’t be captured).

What can we do now?
We could mount the sensor over one of our servos (as in A mobile camera) and with this we can construct a map of the room; this should be a different way to detect changes. When something gets noticed we can scan the space with the camera taking several pictures (or even recording a video; I’ve being avoiding the video until now, but for sure in the future we will try).
Of course, we could have some suggestions or questions here, or see some ideas out there.
There is another remark and it is that the sensor will work even when not enough light is available to take the picture; maybe we could add a light sensor to avoid firing the camera (or, perhaps, illuminate the scene when we are taking a picture).