python 文件读写

[user1@localhost ~]$ ls
Desktop    Downloads  new.txt   Pictures  Templates  test.txt~
Documents  Music      new.txt~  Public    test.txt   Videos
[user1@localhost ~]$ python
Python 2.6.6 (r266:84292, Jul 10 2013, 22:48:45) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-3)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> fnew = open('new.txt','w')
>>> fnew.write('\ntianzhaixing\n')
>>> fnew.close()
>>> fnew = open('new.txt','w')
>>> fnew.write('i love you!')
>>> fnew.close()
>>> fnew = open('new.txt','r+')
>>> fnew.read()
'i love you!'
>>> fnew.write('i am a python leaner.')
>>> fnew.close()
>>> fnew = open('new.txt','r+')
>>> fnew.write('uuu')
>>> fnew.close()
>>> 


[user1@localhost ~]$ ls
Desktop    Downloads  new.txt   Pictures  Templates  test.txt~
Documents  Music      new.txt~  Public    test.txt   Videos
[user1@localhost ~]$ cat new.txt
[user1@localhost ~]$ cat new.txt

tianzhaixing
[user1@localhost ~]$ cat new.txt
[user1@localhost ~]$ cat new.txt
i love you![user1@localhost ~]$ cat new.txt
i love you!i am a python leaner.[user1@localhost ~]$ 
[user1@localhost ~]$ cat new.txt
uuuove you!i am a python leaner.[user1@localhost ~]$