1, global 当某个变量在函数内被声明为global之后，在函数内的修改也会对函数之外的引用产生作用。

#-*-  coding:utf-8 -*-
#global 作用方式
def count(prise):
	global old_prise
	
	new_prise = old_prise+1
	print "old_prise is %d" % old_prise
	old_prise = 20 
	print "new_prise is %d" %new_prise
	return new_prise

old_prise = 10
finally_prise = count(old_prise)
print " global old_prise is %d"%old_prise
print "finally_prise is %d" %finally_prise

2, pass

pass为空语句，与C/C++中的空语句类似

raw_input("Null>")
if Null !== 123
	assert#假如assert不存在则会报错
else:
	print "Null !== 123"

3, yield

yield