python读写文件操作

import os
ls=os.linesep

numlist=['1','2','3']
def getnum():
    num=raw_input('''
    |------------|
    |     1.red  |
    |     2.write|
    |     3.quit |
    |------------|
    Please enter your select num:\n''')
    if num in numlist:
       return num
    else:
       return getnum()

def getfile():
    file=raw_input('enter filename:')
    if file=="":
       return getfile()
    else:
       return file

def getcomment():
    print 'enter comment or quit to exit'
    lines=[]
    while True:
          line=raw_input('>')
          if line=='quit':
             return lines
          else:
             lines.append(line)

def read():
    if os.path.exists(file):
       f=open(file,'r')
       for line in f:
           print line
       f.close()
    else:
       print 'Error:%s not exists' % file
    return getfile()

def write():
    if os.path.exists(file):
       f=open(file,'a')
       f.writelines(['%s%s'%(x,ls) for x in com])
       f.close()
       print 'append'
    else:
       f=open(file,'w')
       f.writelines(['%s%s'%(x,ls) for x in com])
       f.close()
       print 'write to new file'

while True:
    num=getnum()
    if num=='1':
       file=getfile()
       read()
    elif num=='2':
       file=getfile()
       com=getcomment()
       print com
       write()
    else:
       print 'exit'
       break

关于其他文件操作方式
http://www.cnblogs.com/rollenholt/archive/2012/04/23/2466179.html
http://www.cnblogs.com/lovebread/archive/2009/12/24/1631108.html