The following from an interactive session failed instead of just returning the '\x00':

>>> r = csv.reader(['a,line,with,a,null,\x00,byte'])
>>> r.next()

Traceback (most recent call last):
  File "<pyshell#31>", line 1, in -toplevel-
    r.next()
Error: string with NUL bytes
>>> 

Why do you think a CSV reader should support null bytes?
CSV is a text format, not a binary one.

I've been using the csv module to parse data coming from a serial port of a lab instrument. Occasionally the instrument transmits a lone /x00 (maybe when the power cycles, I'm not sure).  Anyhow, I'm now using a try-except statement to catch the error.

I guess my answer to your question is that I think the module should handle whatever string you pass it. Is there a specific reason not to handle /x00?

The core of the csv module is coded in C, so null bytes are as always notoriously problematic when handling strings.
(This is why there's a specific error message only for null bytes.)

I think that the try-except is the sanest solution to this.

If the device is transmitting the occasional spurious you might try wrapping
your file object in  a class which simply deletes any NUL bytes it encounters.

Could someone post a try / except block that handles this.