Caius
Thanks.
I think it was me that asked about one or many scripts to do things.
Going to start working on it in earnest today, I have a pencil with a rubber at the other end, let's see which end wears out quickest.

Posted By: borpinBetter if the clients simply send the data regularly or by exception to a 'static' server.

There have been a couple of comments on this theme. I'd agree in general but practically it might turn out in this case easier to open a port on the sensor machine's net than the central site's, particularly for Steamy's initial demo (because the sensor is on his home network whereas the central machine is in an office with separate IT people) . All a matter of circumstances. The key is not to have the overall design too dependent on the communications details.

I have done a bit, almost working on my home network.
I need to check if I can reach the RPi that is doing the logging at home from the big scary world (I know a cafe with a good view and free wireless). Hopefully I have set up my port forwarding right, guess I will find out if I wake up to no files and plenty of Trojans. Shall pull the lead on the NAS!
I can grab data of the logging RPi from a remote RPi using ssh in a Python script. I have set up passwordless login with RSA, so hopefully I am secure. All passwords have been changed to 'quite tricky ones'. So tricky I keep getting them wrong.

So my Python script on the Office RPi can send a request for data to my Logging RPi and that gets sent back. It prints out to the screen no problem.
Unfortunate when I try and save that data as a .csv file I just get a stream of zeros. There was some message about not being an int value (integer). Need to look at that. Not sure if it is the way the data is transported, or read 'back at the Office'. Just surprised I have got this far without serious upset (writing things down does help).

I lost a day re-writing my CC reading script, was pretty easy once I had finished (dumb mistake not defining it). But now it just logs what I want rather than everything spewing out the CC.
Out of interest, and to save me having a go on something working, can I use 'or' in an if statement. Something like:

If == 100 or 200 or 300

Where would I put the :
After every condition or just at the end?

Off to bed now, not a real programmer, can't live off Red Bull and Pizza.

Thanks for all your help and suggestion.

What cjard says but perhaps the colloquial Python way to do that would be:

if i in (100, 200, 300):

or

if i in {100, 200, 300}:

I.e., using membership testing on a tuple or set. Could use a list, [100, 200, 300], or a dictionary as well if wanted.

Posted By: SteamyTeaChanged the code above as it was total nonsense.

Good, it was. You need to use subprocess.Popen or something to execute a command, you can't just write it in a string.

In general something like "%s" % fandata is pretty meaningless; you might as well just write fandata I'm not quite sure what you had in mind but perhaps it could be done a little more compactly with "%s\n" % fandata

But thinking about it, as I am using cat, I should be able to just write to an existing file as it concatenates. Is that right?

cat concatenates its input files to produce a single output file. (About the only time I use it like that is to concatenate public keys from multiple ssh clients to form the authorized_keys file in the .ssh directory on the host, as I described in email.) To concatenate the output of cat onto an existing file you need to use something else. If it's all on one machine:

cat input1 input2 >> outputadds the contents of the two input files in turn to the output file. Doing redirection like this over ssh or within a Python subprocess.Popen call is more tricky as redirections are handled by the shell (often bash or dash). What I think you want might be done in a shell script on the central data-collection machine using:

ssh pi@192.168.1.100 cat "/home/pi/CurrentCost/oneline.csv" >> /home/pi/RemoteData/oneline.csvYou could get a similar effect in a Python script fairly easily but it would be a few lines of code.

If you were running a script on the sensor machine (the one with the CurrentCost connected) then something like:

cat "/home/pi/CurrentCost/oneline.csv" | ssh steamy@server.charity.org tee --append /home/pi/RemoteData/oneline.csvmight append on the server appropriately - with a few tweaks to the file names.

http://www.theregister.co.uk/2015/02/02/raspberry_pi_model_2/

https://www.modmypi.com/rasclock-raspberry-pi-real-time-clock-module among others?