[Tutor] Defining Exceptions

[Emile van Sebille]

On 2/2/2011 6:51 AM Tom Brauch said...
> All,
>
> I am a python neophyte and not terrible well versed in programming (as will
> become obvious shortly)
>
> I have a script which is reading a serial device on a schedule.  The device
> outputs a header at the beginning of every read.  I have a data file which I
> am appending and would like to eliminate the header so that I end up with
> one master data file.  A copy of the serial readout is:
>
> *
>>
> 6CSV Type Reports2 - Display All Data3 - Display New Data4 - Display Last
> Data5 - Display All Flow Stats6 - Display New Flow Stats7 - Display All
> 5-Min Flow8 - Display New 5-Min Flow9 - Display Error Log>
> 4 - Display CSV DataStation,
> 1Time,Conc(mg/m3),Qtot(m3),no(V),WS(MPS),no(V),RH(%),no(V),AT(C),E,U,M,I,L,R,N,F,P,D,C,T,02/02/11
> 08:00,  0.042, 0.701, 0.004,   0.1, 0.002,     7, 0.012,
> -18.0,0,0,0,0,0,0,0,0,0,0,0,0,
>
> I am only interested in the information following the T, in the header.  I
> have tried to use an exception to have the script throw out all data prior
> to the T, in the header but I don't know how to define this excecption.  My
> current script looks as follows:
>
> def cycle(ser,prefix):
>      inRecovery=False
>      resp=False
> #        tm.sleep(30.0)
>      ser.open()
>      tm.sleep(2)
>      ser.write('\n\r\n\r\n\r')
>      resp=buffer_read(ser)
>
>      ser.write('6')
>      resp=buffer_read(ser)
>
>      ser.write('3')
>      resp=buffer_read(ser)
>      lines = resp.split('\r\n')
>      waste=lines.pop()

pop changes lines by discarding the end of the list.  So your subsequent 
remove fails because waste is no longer in the list.

Perhaps waste is the data you're looking for?

sprinkle some prints through here so you can see what values you're 
dealing with.  That's a common technique to help figure out what's wrong.

HTH,

Emile


>      while True:
>          try:
>              lines.remove(waste)
>          except Exception:
>              ??????
>      for x,row in enumerate(lines):
>          lines[x]=row.split(',')
>      if DEBUG: print lines
>      f=open(prefix,'a')
>      csvf = csv.writer(f)
>      csvf.writerows(lines)
>      f.close()
>      ser.close()
>
> How do I define the exception so that I get only the data following the
> header?
>
> Thanks!
> Tomb
>
>
>
>
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