Python2中的print是一个语句，而Python3中是一个函数
Python2代码 example.py
def greet(name):
print "Hello, {0}!".format(name)
print "What's your name?"
name = raw_input()
greet(name)命令行中执行指令
$ 2to3 -w example.py
Python3代码
def greet(name):
print("Hello, {0}!".format(name))
print("What's your name?")
name = input()
greet(name)书写兼容代码
from __future__ import print_function
