大多数u程序都是：首先接收输入数据，然后按照要求进行处理，最后输出数据
虽然当前数据放在内存中存取的速度要比硬盘中快，但一旦断电则会丢失，所以尽量ctrl+s保持到硬盘中
什么是文件
打开文件
1 open(file, mode='r', buffering=-1, encoding=None,errors=None, newline=None, closefd=True, opener=None)
2
3 open()的第一个参数是传入的文件名，第二个参数是指定文件的打开模式
文件对象方法
1 >>> f = open("D:\\python3.3.2\Hello.txt")
2 >>> f
3 <_io.TextIOWrapper name='D:\\python3.3.2\\Hello.txt' mode='r' encoding='cp936'>
4 >>> f.read()
5 "A. HISTORY OF THE SOFTWARE\n==========================\n\nPython was created in the early 1990s by Guido van Rossum at Stichting\nMathematisch Centrum (CWI, see http://www.cwi.nl) in the Netherlands\nas a successor of a language called ABC. Guido remains Python's\nprincipal author, although it includes many contributions from others.\n\nIn 1995, Guido continued his work on Python at the Corporation for\nNational Research Initiatives (CNRI, see http://www.cnri.reston.va.us)\nin Reston, Virginia where he released several versions of the\nsoftware."
6 >>> f.close()
7 >>> f = open("D:\\python3.3.2\Hello.txt")
8 >>> f.read(5)
9 'A. HI'
10 >>> f.tell() #返回当前光标所在文件的位置
11 5
12 >>> f.readline()
13 'STORY OF THE SOFTWARE\n'
将f放入到列表
1 >>> f = open("D:\\python3.3.2\Hello.txt",'w')#w模式写入会覆盖已存在的文件（即原文件内容全部被删除），a模式则在末尾追加写入
2 >>> f.write('who are you') #返回的是写入的字符数
3 11
4 >>> f.close()
