python if then raise error code example

Example 1: python exception

try:
  # code block
except ValueError as ve:
  print(ve)

Example 2: python file open try except error

def FileCheck(fn):
    try:
      open(fn, "r")
      return 1
    except IOError:
      print "Error: File does not appear to exist."
      return 0

result = FileCheck("testfile")
print result