/* while 是在有条件控制的情况下 进行的循环 */

[root@localhost test1]# vim .py

//ADD

#!/usr/bin/python

n =

while True:

    if n == :

        break

    print n, 'hello'

    n += 

[root@localhost test1]# python .py

 hello

 hello

 hello

 hello

 hello

 hello

 hello

 hello

 hello

 hello

[root@localhost test1]# vim .py

//ADD

#!/usr/bin/python

while True:

    print 'hello'

    input = raw_input("Please input something.q for quit: ")

    if input == "q":

        break

[root@localhost test1]# python .py

hello

Please input something.q for quit: e

hello

Please input something.q for quit: r

hello

Please input something.q for quit: t

hello

Please input something.q for quit: f

hello

Please input something.q for quit: q

[root@localhost test1]# vim .py

//add

#!/usr/bin/python

x = ''

while x != 'q':

    print 'hello'

    x = raw_input("Please input something, q for quit: ")

/* 首先，要给x定义一个初始值，

    然后再继续执行。 这里没有定义输入q后会有什么结果，

    但是执行后，输入q则自动退出

*/

[root@localhost test1]# python .py

hello

Please input something, q for quit: s

hello

Please input something, q for quit: s

hello

Please input something, q for quit: d

hello

Please input something, q for quit: f

hello

Please input something, q for quit: g

hello

Please input something, q for quit: q

/* 先创建一个文件 */

[root@localhost tmp]# cat 1.txt

1111

//先用一个变量定义，这个变量对应什么文件

In [1]: ll = open('/tmp/1.txt')

In [2]: ll

Out[2]: <open file '/tmp/1.txt', mode 'r' at 0x99d81d8>

//将这个文件或变量打开，并赋予w权限

In [4]: ll = open('/tmp/1.txt', 'w')

//写变量。括号里为写的内容，此处写的内容会覆盖原来的内容

In [5]: ll.write("aa")

[root@localhost tmp]# cat 1.txt

aa[root@localhost tmp]#

/* 有时，需要需要将变量关掉才可以执行看到改变 */

/* 再一次打开python的界面需要重新定义变量。*/

In [2]: ll = open('/tmp/1.txt')

In [3]: ll.read()　　　　//从最开始读

Out[3]: 'aa'

In [4]: ll.read()　　　　//当第二次读取时，指针已经读完了前面的内容，就只剩空了

Out[4]: ''

/* 读取的具体内容 */

//1. 输入需要读取的 前几个字符

[root@localhost tmp]# cat 1.txt

abc

sjdh[root@localhost tmp]#

In [1]: ll = open('/tmp/1.txt' , 'r')

In [2]: ll

Out[2]: <open file '/tmp/1.txt', mode 'r' at 0x9392180>

In [3]: ll.read(2)

Out[3]: 'ab'

// 2.读取一行

In [1]: ll = open('/tmp/1.txt')

In [2]: ll.readline()

Out[2]: 'abc\n'

// 3.读取多行（有多少行读多少行），并且返回一个list

// 4. next() 可对一个文件一行一行的读取

In [5]: ll = open('/tmp/1.txt')

In [6]: ll.readlines()

Out[6]: ['abc\n', 'sjdh']

In [1]: ll = open('/tmp/1.txt')

In [2]: ll.next()

Out[2]: 'abc\n'

In [3]: ll.next()

Out[3]: 'sjdh'

In [4]: ll.next()

---------------------------------------------------------------------------

StopIteration                             Traceback (most recent call last)

<ipython-input-4-e9a4e3e4293f> in <module>()

----> 1 ll.next()

StopIteration:

/* python脚本，对文件进行遍历 */

[root@localhost test1]# vim 16.py

//ADD

#!/usr/bin/python

ll = open('/tmp/1.txt')

for line in ll.readlines():

    print line,

[root@localhost test1]# python 16.py

abc

sjdh