Changing Number Format

[moby]

I'm strictly a hardware type and am caught in a conundrum trying to capture data from my oscilloscope.
I know nothing about Python, but found a workable solution on EEVblog.
Sample code which samples Channel 1 and writes to a CSV file :

   # Read DS1054Z Channel 1
    telnetToInstrument.write(":MEAS:ITEM? VAVG, CHAN1\n")
    buff = telnetToInstrument.read_until("\n", maxWaitForAnswer)
    csvLine += "," + buff[:-1]

Now this works just fine but has one problem :
It writes in scientific notation (nnnEXPmmm)
Which is really hard to read (logging the output of a photovoltaic panel)
How can I make it write in standard decimal ie NN.NN (13.65 volts for instance)
Any help appreciated.
Thanks, Mike