http://docs.python.org/library/2to3.html#using-2to3 contains an example.py sample which is claimed to be Python 2.x source, but that's not true:

def greet(name):
    print "Hello, {0}!".format(name)
print "What's your name?"
name = raw_input()
greet(name)

The code is valid only for Python 2.6+. For previous versions it gives the following traceback:

Traceback (most recent call last):
  File "ewe.py", line 5, in <module>
    greet(name)
  File "ewe.py", line 2, in greet
    print "Hello, {0}!".format(name)
AttributeError: 'str' object has no attribute 'format'