print <__main__.Pair object at 0x7fd39d2c26d8> code example

Example 1: if __name__ == '__main__'

if __name__ == "__main__":

Example 2: __name__== __main__ in python

# If the python interpreter is running that module (the source file)
# as the main program, it sets the special __name__ variable to have
# a value “__main__”. If this file is being imported from another 
# module, __name__ will be set to the module’s name.
if __name__=='__main__':
  # do something