Python Basics (4)--file object, pointer, Os,os.path module

in [105]:F1 = open ('/tmp/passwd ', ' r+ ') read/write mode on

in [106]: F1.next () read a line, next read down, will not move the line indicator

OUT[106]: ' root:x:0:0:root:/root:/bin/bash\n '

In [107]: F1.seek (0,2) offset from the end of the file line (2) position 0 (0), F1.seek (0) back to the beginning

In [109]: F1.tell () View file location (bytes)

OUT[109]: 1576

in [+]: F1.write (' New line.\n ') Add a line

In [F1.readline]: read one line, move line indicator

OUT[112]: "

In [129]: F1.closed decide whether to close

OUT[129]: False No

In [up]: F1.close () Close

In [133]: f1.closed

OUT[133]: True is

Example: Writes the result of a power operation from 1 to 10 to Test.txt

F1 = open ('/tmp/test.txt ', ' w+ ')

For i**2-I in Range (1,11):

F1.write (str (line) + ' \ n ')

F1.flush ()

F1.close ()

Writes directory/ext The file list results to a file test1.txt

F1 = open ('/tmp/test1.txt ', ' w+ ')

Import OS

L1 = Os.listdir (' etc ') #列出目录下的文件

F1.writelines (L1) #将字符串列表内容写入到文件, cannot write data of type Integer.

F1.flush ()

F1.close ()

Note: If you want to add a newline character \ n to each file, you can define it as follows:

F3=open ('/tmp/test3.txt ', ' w+ ')

L2 = [i+ ' \ n ' for I in Os.listdir (' etc ')]

F3.writelines (L2)

Example: input content to file

#!/usr/local/bin/python27

#

Import OS

Import Os.path #加载模块

Filename= '/tmp/test.txt '

If Os.path.isfile (filename): #判断是否有文件filename

f1 = open (filename, ' A + ') #追加打开模式

While True:

line = Raw_input (' Enter something>> ') #交互输入模式

if line = = ' Q ' or line = = ' Quit ':

Break

F1.write (line+ ' \ n ')

F1.close ()

Example: Pointers

Pointer: Open a file, iterate print, the pointer will go to the end, the second time you print, you need to restore the pointer to the beginning

In [2]: f1 = open ('/etc/passwd ', ' R ')

In [3]: F1:

...: Print line,

...: print ' =================== '

...:

Root:x:0:0:root:/root:/bin/bash

===================

Bin:x:1:1:bin:/bin:/sbin/nologin

===================

Daemon:x:2:2:daemon:/sbin:/sbin/nologin

In [5]: F1.tell ()

OUT[5]: 1576

In [6]: F1.seek (0) #需要将指针恢复到最开始

In [7]: F1:

Print line,

print ' =================== '

...:

Root:x:0:0:root:/root:/bin/bash

===================

Python Basics (4)--file object, pointer, Os,os.path module