I have used OpenCv within my Windows applications in the past and in this case, an application would be built and installed as a Windows Service so that it could be set to start automatically and start running. Differences are I have done these in compiled languages and we were on Windows.
Now, I am playing around with porting the application to run on Linux/Raspberry Pi. The application simply gets a video feed, does some object detection using OpenCv and then sends result via HTTP web api.
First comment before my question is (I am still getting familiar with this setup) it seems that Python is by far the language of choice for all of this. However, the end goal is to have this device be headless (no monitor or input devices and act like an IoT device) so I don't need or better, can't open a console and type commands.
So, for the question, what is the equivalent to a Windows Service on Raspberry Pi so that my application just starts up on boot and runs as long as the device is on? The subjective follow up question is Python still a good choice considering everything I have described above or would I be better off doing a full blown compiled app in c or c++?
Thanks!
If you are using Raspbian, then I would say the easiest tool il systemd (daemon) and the systemctl (shell command).
In order to run your python script as a daemon (a daemon is what Windows calls "Service") is to create a configuration file named .service and put it in the /etc/systemd/system path.
To get an idea of how to configure the file, you can take this example:
[Unit]
Description=Your service name
[Service]
ExecStart=python <path to python script>
StandardOutput=null
[Install]
WantedBy=multi-user.target
Alias=this_script_name>.script
Hope it helps!
Check out Supervisor: http://supervisord.org/. It should do what you need to do in terms of running your program on boot and restarting if it crashes, etc.
I don't have any experience with OpenCV, but web app frameworks like Flask (http://flask.pocoo.org/) make it very easy to expose an HTTP API with minimal code.
Good luck!
Related
I have a python script that checks the temperature every 24 hours, is there a way to leave it running if I shut the computer down/log off.
Shutdown - no.
Logoff - potentially, yes.
If you want to the script to automatically start when you turn the computer back on, then you can add the script to your startup folder (Windows) or schedule the script (Windows tasks, cron job, systemd timer).
If you really want a temperature tracker that is permanently available, you can use a low-power solution like the Raspberry Pi rather than leaving your pc on.
The best way to accomplish this is to have your program run on some type of server that your computer can connect to. A server could be anything from a raspberry pi to an old disused computer or a web server or cloud server. You would have to build a program that can be accessed from your computer, and depending on the server and you would access it in a lot of different ways depending the way you build your program and your server.
Doing things this way means your script will always be able to check the temperature because it will be running on a system that stays on.
Scripts are unable to run while your computer is powered off. What operating system are you running? How are you collecting the temperature? It is hard to give much more help without this information.
One thing I might suggest is powering on the system remotely at a scheduled time, using another networked machine.
You can take a look at the following pages
http://www.wikihow.com/Automatically-Turn-on-a-Computer-at-a-Specified-Time
http://lifehacker.com/5831504/how-can-i-start-and-shut-down-my-computer-automatically-every-morning
Additionally once it turn on, you can perform a cronjob, for execute your python code by a console command >> python yourfile.py . What is the Windows version of cron?
I am writing a test application in python and to test some particular scenario, I need to launch my python child process in windows SYSTEM account.
I can do this by creating exe from my python script and then use that while creating windows service. But this option is not good for me because in future if I change anything in my python script then I have to regenerate exe every-time.
If anybody have any better idea about how to do this then please let me know.
Bishnu
Create a service that runs permanently.
Arrange for the service to have an IPC communications channel.
From your desktop python code, send messages to the service down that IPC channel. These messages specify the action to be taken by the service.
The service receives the message and performs the action. That is, executes the python code that the sender requests.
This allows you to decouple the service from the python code that it executes and so allows you to avoid repeatedly re-installing a service.
If you don't want to run in a service then you can use CreateProcessAsUser or similar APIs.
You could also use Windows Task Scheduler, it can run a script under SYSTEM account and its interface is easy (if you do not test too often :-) )
To run a file with system account privileges, you can use psexec. Download this :
Sysinternals
Then you may use :
os.system
or
subprocess.call
And execute:
PSEXEC -i -s -d CMD "path\to\yourfile"
Just came across this one - I know, a bit late, but anyway. I encountered a similar situation and I solved it with NSSM (Non_Sucking Service Manager). Basically, this program enables you to start any executable as a service, which I did with my Python executable and gave it the Python script I was testing on as a parameter.
So I could run the service and edit the script however I wanted. I just had to restart the service when I made any changes to the script.
One point for productive environments: Try not to rely on third party software like NSSM. You could also achieve this with the standard SC command (see this answer) or PowerShell (see this MS doc).
I am currently developing an open source software based on python/django. The software should later be easy installable by a standard windows/linux users without any programming experiance. It should also be portable to different computers. The only installation that should be required on these computers should be python itself.
Is there a way to get this to work?
I already found this "dbuilder" Django Projects as Desktop applications : how to?
desktop-applications-how-to
It seems to be a bit outdated and not a very smooth solution.
Are there better solutions?
Just use a portable version of python on your memory stick. Make a batch file that runs
projname.bat file:
python.exe /django-app-path/manage.py runserver
now open a browser and browse for it
the default address will be:
http://127.0.0.1:8000
If you need to browse your app on other device that you're app is running:
get your server ip with
windows shell>ipconfig
linux shell# ifconfig
then run your development server on that address (in the batch file):
python.exe /django-app-path/manage.py runserver your-ip-address:port-if-not-80
I wrote a code using python and dogtail (automation program from redhat) to automate a program. This program is running in a virtual machine without desktop graphical environment.
I ssh the virtual machine and run the program and the graphical interface start on my machine.
I then run my python program on my machine to automate this program. And here is the problem... the python code does not work because it did not recognize the remote program that is run via ssh. And if I move the python code to the virtual machine it asks me to enable the “assistive technologies” and I can’t because I do not have gnome or any graphical environment in the virtual machine?
All used operating systems are Ubuntu…
I try to find solution everywhere without success. I wish I explain the problem clearly, if not please let me know...
Please help… thank you
There is a dogtail-run-headless-next binary in dogtail and it should be able to start X (or more precisely gdm service) and log in (with autologin of test user). Then it's parameter is executed in desktop environment.
we use (under root)
sudo -u test dogtail-run-headless-next "./your_script"
I hope this will enable assistive technology, too. If not you can always use:
if not isA11yEnabled():
enableA11y(True)
You can automate ssh into a machine via pexpect. See new: http://pexpect.readthedocs.org/en/latest/api/pxssh.html
or older:
http://pexpect.sourceforge.net/pexpect.html
I'm looking to use a local webserver to run a series of python scripts for the user. For various unavoidable reasons, the python script must run locally, not on a server. As a result, I'll be using HTML+browser as the UI, which I'm comfortable with, for the front end.
I've been looking, therefore, for a lightweight web server that can execute python scripts, sitting in the background on a machine, ideally as a Windows service. Security and extensibility are not high priorities as it's all running internally on a small network.
Should I run a native python webserver as a Windows service (in which case, how)? Or is it just as easy to install Apache onto the user's machine and run as CGI? Since this is all local, performance is not an issue either.
Or am I missing something obvious?
Don't waste a lot of time creating Windows service.
Don't waste a lot of time on Windows Apache.
Just make a Python service that responds to HTTP requests.
Look at https://docs.python.org/2/library/basehttpserver.html
https://docs.python.org/3/library/http.server.html for version 3
Python offers an HTTP server that you can extend with your server-side methods.
Look at http://docs.python.org/library/wsgiref.html
Python offers a WSGI reference implementation that makes your server easy and standards-compliant.
Also http://fragments.turtlemeat.com/pythonwebserver.php
"I'm trying to avoid making the user run python stuff from the command prompt."
I don't see how clicking a web page is any different from clicking desktop icons.
Starting a web server based on Python is relatively easy, once you have the web server. First, build the server. Later, you can make sure the server starts. Let's look at some ways.
Your user can't use a random browser to open your local page. They need a bookmark to launch "localhost:8000/myspecialserverinsteadofthedestop/" That bookmark can be a .BAT file that (1) runs the server, (2) runs firefox with the proper initial URL.
You can put the server in the user's start-this menu.
You can make your Python program a windows "service".
Best way is to make your own local server by using command prompt.
Make a new folder say Project
Make a new folder inside project & name it as "cgi-bin"(without quotes)
Paste your .py file inside the cgi-bin folder
Open cmd and change to the directory from which you want to run the server and type "python -m CGIHTTPServer"(without quotes)
Minimize the cmd window & open your browser and type "localhost:8000/cgi-bin/yourpythonfilename.py"(without quotes).
The wasiest step would be navigate to folder where your files are located and running http.server module
cd /yourapp
python3 -m http.server
the you should see something like this in console
Serving HTTP on 0.0.0.0 port 8000 (http://0.0.0.0:8000/) ...
Running a native python webserver as a windows service should be a no brainer. Check out the documentation for writing windows services (win32api, ActiveState python) in python and also the documentation for subclassing BaseHttpServer and SimpleHttpServer.
BTW: I had a similar question on stackoverflow: How to stop BaseHTTPServer.serve_forever() in a BaseHTTPRequestHandler subclass?
Basically, you subclass BaseHTTPServer (you have to anyway...) and then... but just read the accepted answer - it set me on the right track!