how to use try and catch in python code example

Example 1: throwing an exception python

raise Exception("message")

Example 2: try catch in python

try:
  print("try to run this block")
except:
  print("run this bock if there was error in earlier block")

Example 3: 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