Python3.x与Python2.x的差异用法
1，Python2.x：import urllib2
Python3.x：import urllib.request
2，Python2.x： urllib2.URLError, e:
Python3.x：urllib.request.URLError as e:
3，Python2.x：print ‘hello world‘
Python3.x： print(‘hello world‘)
4，Python2.x：有raw_input和input
Python3.x：将raw_input和input进行了整合，只有input