Pulling Data from Python Script for Webpage on RPi

Question

Now this issue isn't particular to the Raspberry Pi, but I'm really lost on how all this works. I've written a Python script that successfully pulls the temperature and humidity from a number of DHT22 modules, averages them, then prints them. From here, how do I port this information to my webpage to be displayed? I have absolutely no idea how I would connect the return values of my Python script to an HTML file, or how to make it update every time the Python script computes the temperature/humidity, which is done every two seconds.

I've seen frameworks like Django, but does it allow me to access the GPIO pins on the RPi in the script?

• goldilocks: Web frameworks allow you to do whatever the interface language (in this case python) can do on the server.

Answer 1

You can run your Python script as CGI from the web server, all outputs from the script has to be formatted as HTML. Or can save fetched values in a text file or in MySQL or SQLite database and grab the values from script in the web server (could be also Python or Php or something else)

Answer 2

I really enjoy using websockets for my realtime data in the Pi. I would convert your DHT22 into what this blog considers a "module" http://simplyautomationized.blogspot.com/2015/09/raspberry-pi-create-websocket-api.html

Put your DHT code into a class that is on another "thread":

class DHT_Poller(threading.Thread):
 cmd = None
 def __init__(self):
 threading.Thread.__init__(self)
 self.dht_temp_change_callback = None
 self.loop = True
 self.dht_temp = -1
 def run(self):
 while(self.loop):
 dht = get_temp_dht() # your python method
 if(dht!=self.dht_temp): #means your temperature has changed
 self.dht_temp=dht
 if(self.dht_temp_change_callback):
 self.dht_temp_change_callback(json.dumps({"Temp":dht}))
 def stop(self):
 self.loop=False
 def get_temp(self):
 return self.dht_temp

• Save that into a file and import it into your websocket server.
• Follow the step on the blog to build the websocket/website server.
• Build a simple webpage that connects to the websocket server. Update values on the webpage using jquery. the github example of the blog is here: https://github.com/SimplyAutomationized/PiFacePythonWebSocket/blob/master/websocket.py