what's this instance?

[J. Peng]

def safe_float(object):
  try:
    retval = float(object)
  except (ValueError, TypeError), oops:
    retval = str(oops)
  return retval

x=safe_float([1,2,3,4])
print x


The code above works well.But what's the instance of "oops"? where is it
coming from? I'm totally confused on it.thanks.
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