#Open your file
  try:
    #Write data to your file
  finally:
   file.close()

#使用write()写文件 
file_obj=open('test.txt','w') 
str1='hello\n' 
str2='world\n' 
str3='python' 
file_obj.write(str1) 
file_obj.write(str2) 
file_obj.write(str3) 
file_obj.close() 
#使用writelines()写文件 
file_obj=open('test.txt','w') 
str1='hello\n' 
str2='world\n' 
str3='python' 
file_obj.writelines([str1,str2,str3]) 
file_obj.close() 
#输出 本地test.txt文件 
hello 
word 
python 

#使用read 
print 'Use the read' 
file_obj=open('test.txt','r') 
s=file_obj.read() 
print s 
file_obj.close 
#使用readline 
print 'Use the readline' 
file_obj=open('test.txt','r') 
line1=file_obj.readline() 
line1=line1.rstrip('\n') 
print 'l1 ',line1 
line2=file_obj.readline() 
line2=line2.rstrip('\n') 
print 'l2 ',line2 
line3=file_obj.readline() 
line3=line3.rstrip('\n') 
print 'l3 ',line3 
file_obj.close 
#使用readlines 
print 'Use the readlines' 
file_obj=open('test.txt','r') 
li=file_obj.readlines() 
print li 
file_obj.close 

Use the read 
hello 
world 
python 
Use the readline 
l1 hello 
l2 world 
l3 python 
Use the readlines 
['hello\n', 'world\n', 'python'] 

#格式化写入 
fd=open('format.txt','w') 
head="%-8s%-10s%-10s\n"%('Id','Name','Record') 
fd.write(head) 
item1="%-8d%-10s%-10.2f\n"%(10001,'Eastmount',78.9) 
fd.write(item1) 
item2="%-8d%-10s%-10.2f\n"%(10002,'CSDN',89.1234) 
fd.write(item2) 
fd.close() 
#输出 
Id  Name  Record  
10001 Eastmount 78.90  
10002 CSDN  89.12 

#使用while循环 
fr=open('test.txt','r') 
str=fr.readline() 
str=str.rstrip('\n') 
while str!="": 
 print str 
 str=fr.readline() 
 str=str.rstrip('\n') 
else: 
 print 'End While' 
fr.close 
#使用for循环 
rfile=open('test.txt','r') 
for s in rfile: 
 s=s.rstrip('\n') 
 print s 
print 'End for' 
rfile.close() 

 s='www.csdn.NET'
  si=iter(s)   #生成迭代器
  print si.next() #调用next依次获取元素,最后迭代器没有返回值时引发StopIteration异常