Python Cookbook (2) 文件

1. Python对文件的支持
1）内建的open函数等
2） os
3）第三方工具
有些语言的特点就是很容易支持第三方

2. Python中的大多数文件接口都是跨平台的。这种设计的重要性怎么赞美也不为过。

3. Python的文件处理接口往往并不局限在只用于真实的物理文件，只要目标对象实现了期望的协议，一切工作都可以平滑自然地进行。

4. 大文件的时候怎么处理？

5. open 的读取模式
r 以文本读取，默认，不用指定
rb 以二进制读取
w 以文本模式写
wb 以二进制写
rU 同r，但是考虑了不用平台的\n，用这个就对了

Example：

 1 def test_file():
 2     filename = "./main.py"
 3     infile = open(filename, 'rU');
 4     try:
 5         #for line in infile:
 6         lines = len(infile.readlines())
 7         print "{0}(line={1})".format(filename, lines);
 8     finally:
 9         infile.close()
10     infile.close()
11     
12     outfilename = "./testfile.txt"
13     outfile = open(outfilename, 'w')
14     outfile.write("This is a test file");
15     outfile.close()

tar 工具

 1 #!/usr/local/bin/python
 2 
 3 import os
 4 import tarfile
 5 import sys
 6 
 7 def make_tar(folder_to_backup, dest_folder='.', compression='gz'):
 8     if compression:
 9         dest_ext='.'+compression
10     else:
11         dest_ext=''
12     arcname = os.path.basename(folder_to_backup)
13     dest_name = '{0}.tar{1}'.format(arcname, dest_ext)
14     dest_path = os.path.join(dest_folder, dest_name)
15     if compression:
16         dest_cmp = ':' + compression
17     else:
18         dest_cmp = ''
19     
20     out = tarfile.TarFile.open(dest_path, 'w'+dest_cmp)
21     out.add(folder_to_backup, arcname)
22     out.close()
23     return dest_path
24     
25 def main():
26     argc = len(sys.argv)
27     folder_to_backup = ''
28     dest_folder = ''
29     compression = ''
30        
31     if argc == 2: 
32         folder_to_backup = sys.argv[1]
33         make_tar(folder_to_backup)
34     
35     elif argc == 3:
36         folder_to_backup = sys.argv[1]
37         dest_folder = sys.argv[2]
38         make_tar(folder_to_backup, dest_folder)
39     
40     elif argc == 4:
41         folder_to_backup = sys.argv[1]
42         dest_folder = sys.argv[2]
43         compression = sys.argv[3]
44         make_tar(folder_to_backup, dest_folder, compression)
45     else:
46         print "Args wrong, ./mytar folder_to_backup [dest_folder [compression]]"
47         return
48     
49     return
50     
51 main()