import sys 
 
f=open('test.txt','a+') 
a='123' 
b='456' 
print >> f,a,b 
f.close() 

import sys 
 
f=open('a.txt','w') 
old=sys.stdout #将当前系统输出储存到临时变量 
sys.stdout=f #输出重定向到文件 
print 'Hello World!' #测试一个打印输出 
sys.stdout=old  #还原系统输出 
f.close() 
print open('a.txt','r') # 错误的方法，仅用于查看输出，了解python 
print open('a.txt','r').read() 

import sys 
year=1 
years=15 
bj=10000 
rate=0.05 
f=open('total.txt','w+') 
while year < years: 
   bj=bj*(1+rate) 
   print >> f,"第%d年，本息合计%0.2f" % (year,bj) 
   year+=1 

class FakeOut: 
 def __init__(self): 
  self.str='' 
  self.n=0 
 def write(self,s): 
  self.str+="Out:[%s] %s\n"%(self.n,s) 
  self.n+=1 
 def show(self): #显示函数，非必须 
  print self.str 
 def clear(self): #清空函数，非必须 
  self.str='' 
  self.n=0 
f=FakeOut() 
import sys 
old=sys.stdout 
sys.stdout=f 
print 'Hello weird.' 
print 'Hello weird too.' 
sys.stdout=old 
f.show() 
# 输出： 
# Out:[0] Hello weird. 
# Out:[1] 
 
# Out:[2] Hello weird too. 
# Out:[3]