文章来自《Python cookbook》.

文章来自《[b]Python cookbook》. [/b]
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-- 218.25.65.133 [2004-09-30 04:40:07]

目录

描述

问题 Problem

解决 Solution

讨论 Discussion

参考 See Also

1. 描述

Computing Directory Sizes in a Cross-Platform Way
平台无关地计算目录大小
Credit: Frank Fejes

1.1. 问题 Problem

You need to compute the total size of a directory (or set of directories) in a way that works under both Windows and Unix-like platforms.
需要计算目录(或者目录集合)的大小，要求在Windows和类Unix系统上代码都适用。

1.2. 解决 Solution

There are easier platform-dependent solutions, such as Unix's du, but Python also makes it quite feasible to have a cross-platform solution:
特定平台上有简单的方法，如Unix上的du命令。使用Python可以更容易的获得平台无关的方法：

1 import os
2 from os.path import *
3
4 class DirSizeError(Exception): pass
5
6 def dir_size(start, follow_links=0, start_depth=0, max_depth=0, skip_errs=0):
7
8     # Get a list of all names of files and subdirectories in directory start
9     try: dir_list = os.listdir(start)
10     except:
11         # If start is a directory, we probably have permission problems
12         if os.path.isdir(start):                                    #译注：没有读权限
13             raise DirSizeError('Cannot list directory %s'%start)
14         else:  # otherwise, just re-raise the error so that it propagates
15             raise
16
17     total = 0L
18     for item in dir_list:
19         # Get statistics on each item--file and subdirectory--of start
20         path = join(start, item)
21         try: stats = os.stat(path)
22         except:
23             if not skip_errs:
24                 raise DirSizeError('Cannot stat %s'%path)           #译注：没有读权限
25         # The size in bytes is in the seventh item of the stats tuple, so:
26         total += stats[6]
27         # recursive descent if warranted
28         if isdir(path) and (follow_links or not islink(path)):      #译注：遍历计算子目录
29             bytes = dir_size(path, follow_links, start_depth+1, max_depth)
30             total += bytes
31             if max_depth and (start_depth < max_depth):
32                 print_path(path, bytes)
33     return total
34
35 def print_path(path, bytes, units='b'):
36     if units == 'k':
37         print '%-8ld%s' % (bytes / 1024, path)
38     elif units == 'm':
39         print '%-5ld%s' % (bytes / 1024 / 1024, path)
40     else:
41         print '%-11ld%s' % (bytes, path)
42
43 def usage (name):
44     print "usage: %s [-bkLm] [-d depth] directory [directory...]" % name
45     print '/t-b/t/tDisplay in Bytes (default)'
46     print '/t-k/t/tDisplay in Kilobytes'
47     print '/t-m/t/tDisplay in Megabytes'
48     print '/t-L/t/tFollow symbolic links (meaningful on Unix only)'
49     print '/t-d, --depth/t# of directories down to print (default = 0)'
50
51 if _ _name_ _=='_ _main_ _':
52     # When used as a script:
53     import string, sys, getopt
54
55     units = 'b'
56     follow_links = 0
57     depth = 0
58
59     try:
60         opts, args = getopt.getopt(sys.argv[1:], "bkLmd:", ["depth="])           #译注：解析命令行参数
61     except getopt.GetoptError:
62         usage(sys.argv[0])
63         sys.exit(1)
64
65     for o, a in opts:
66         if o == '-b': units = 'b'
67         elif o == '-k': units = 'k'
68         elif o == '-L': follow_links = 1
69         elif o == '-m': units = 'm'
70         elif o in ('-d', '--depth'):
71             try: depth = int(a)
72             except:
73                 print "Not a valid integer: (%s)" % a
74                 usage(sys.argv[0])
75                 sys.exit(1)
76
77     if len(args) < 1:
78         print "No directories specified"
79         usage(sys.argv[0])
80         sys.exit(1)
81     else:
82         paths = args
83
84     for path in paths:
85         try: bytes = dir_size(path, follow_links, 0, depth)
86         except DirSizeError, x: print "Error:", x
87         else: print_path(path, bytes)

1.3. 讨论 Discussion

Unix-like platforms have the du command, but that doesn't help when you need to get information about disk-space usage in a cross-platform way. This recipe has been tested under both Windows and Unix, although it is most useful under Windows, where the normal way of getting this information requires using a GUI. In any case, the recipe's code can be used both as a module (in which case you'll normally call only the dir_size function) or as a command-line script. Typical use as a script is:
类Unix 平台上可以使用du命令计算目录大小，但是在其它平台上没有这个命令。上面脚本在Windows和Unix下都测试过。在Windows下面计算目录大小 信息通常需要使用GUI(?)，这样脚本在windows下更有用些. 在任何平台下，脚本代码可以作为一个模块(可能仅仅使用dir-size函数)或者作为命令行脚本使用。 典型的使用方法如下：

C:/> python dir_size.py "c:/Program Files"

This will give you some idea of where all your disk space has gone. To help you narrow the search, you can, for example, display each subdirectory:
使用上面命令行脚本可以获得全部磁盘空间的使用情况。如果想获得每个子目录的信息，可以使用浅搜索:

C:/> python dir_size.py --depth=1 "c:/Program Files"

The recipe's operation is based on recursive descent. os.listdir provides a list of names of all the files and subdirectories of a given directory. If dir_size finds a subdirectory, it calls itself recursively. An alternative architecture might be based on os.path.walk, which handles the recursion on our behalf and just does callbacks to a function we specify, for each subdirectory it visits. However, here we need to be able to control the depth of descent (e.g., to allow the useful --depth command-line option, which turns into the max_depth argument of the dir_size function). This control is easier to attain when we administer the recursion directly, rather than letting os.path.walk handle it on our behalf.
脚 本代码中使用下向递归。os.listdir获得指定目录下所有文件名称和子目录名称的list。如果函数dir_size判断出一个子目录，会递归调用 自己。另一种解决方法是以os.path.walk为基础，walk代替我们处理递归，在每个子目录上使用我们指定的回调函数获得目录大小信息。不过，这 里我们需要控制递归的深度(比如，允许使用便利的命令行参数--depth来确定dir_size函数的参数max_depth)，直接处理递归而不用 os.path.walk代替我们处理， 可以更容易的控制函数行为。

1.4. 参考 See Also

Documentation for the os.path and getopt modules in the Library Reference.