一、print，在python3中已经是函数

>>> import sys>>> print("fatal error",file=sys.stderr)fatal error>>> fp=open(r"d:\\a.txt",'w')>>> print("python3",file=fp)>>> fp.close()>>> print("There are <", 2**32, "> possibilities!", sep=" ") 默认空格符为分隔符There are < 4294967296 > possibilities!>>> print("There are <", 2**32, "> possibilities!", sep="") 自定义，不用空格分开There are <4294967296> possibilities!>>>

二、python3中是unicode码，而python2中是ascii码，可以避免中文的编码困扰

>>> import sys>>> print(sys.getdefaultencoding())utf-8>>> "中文"'中文'

在python2.7中

>>> import sys>>> sys.getdefaultencoding()'ascii'>>> "中文"'\xd6\xd0\xc\xc4'

三、定义变量更灵活

>>> a,*b,c= range(5)>>> a,b,c(0, [1, 2, 3], 4)

四、某些库改名了

Old Name New Name

_winreg winreg

ConfigParser configparser

copy_reg copyreg

Queue queue

SocketServer socketserver

markupbase _markupbase

repr reprlib

test.test_support test.support