8. Python自定义模块humansize

我们在提取一个文件元信息的时候，经常会使用到获取元信息的size， 但是默认提取出来的是字节为单位计算的大小，我们需要转换成MB或者GB 或者TB的大小。

因此就需要使用到humansize这个模块， 这个模块不是系统内置的， 你可以通过help（）查询内置模块是没有这个的模块的。 需要从其他地方导入才可以进行使用。

将下面的文件保存成humansize.py 放在默认python目录下。

 1 ‘‘‘‘‘Convert file sizes to human-readable form.
 2
 3 Available functions:
 4 approximate_size(size, a_kilobyte_is_1024_bytes)
 5     takes a file size and returns a human-readable string
 6
 7 Examples:
 8 >>> approximate_size(1024)
 9 ‘1.0 KiB‘
10 >>> approximate_size(1000, False)
11 ‘1.0 KB‘
12
13 ‘‘‘
14
15 SUFFIXES = {1000: [‘KB‘, ‘MB‘, ‘GB‘, ‘TB‘, ‘PB‘, ‘EB‘, ‘ZB‘, ‘YB‘],
16             1024: [‘KiB‘, ‘MiB‘, ‘GiB‘, ‘TiB‘, ‘PiB‘, ‘EiB‘, ‘ZiB‘, ‘YiB‘]}
17
18 def approximate_size(size, a_kilobyte_is_1024_bytes=True):
19     ‘‘‘‘‘Convert a file size to human-readable form.
20
21     Keyword arguments:
22     size -- file size in bytes
23     a_kilobyte_is_1024_bytes -- if True (default), use multiples of 1024
24                                 if False, use multiples of 1000
25
26     Returns: string
27
28     ‘‘‘
29     if size < 0:
30         raise ValueError(‘number must be non-negative‘)
31
32     multiple = 1024 if a_kilobyte_is_1024_bytes else 1000
33     for suffix in SUFFIXES[multiple]:
34         size /= multiple
35         if size < multiple:
36             return ‘{0:.1f} {1}‘.format(size, suffix)
37
38     raise ValueError(‘number too large‘)
39
40 if __name__ == ‘__main__‘:
41     print(approximate_size(1000000000000, False))
42     print(approximate_size(1000000000000))
43
44 # Copyright (c) 2009, Mark Pilgrim, All rights reserved.
45 #
46 # Redistribution and use in source and binary forms, with or without modification,
47 # are permitted provided that the following conditions are met:
48 #
49 # * Redistributions of source code must retain the above copyright notice,
50 #   this list of conditions and the following disclaimer.
51 # * Redistributions in binary form must reproduce the above copyright notice,
52 #   this list of conditions and the following disclaimer in the documentation
53 #   and/or other materials provided with the distribution.
54 #
55 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ‘AS IS‘
56 # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
57 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
58 # ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
59 # LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
60 # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
61 # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
62 # INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
63 # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
64 # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
65 # POSSIBILITY OF SUCH DAMAGE. 

 该程序的功能是将以字节为单位的文件大小转换为以更易读形式，如将1024 B转换为1KB

 1 >>> import sys
 2 >>> import os
 3 >>> metadata = os.stat(‘test.docx‘)
 4 >>> metadata
 5 nt.stat_result(st_mode=33206, st_ino=0L, st_dev=0L, st_nlink=0, st_uid=0, st_gid=0, st_size=4934265L, st_atime=1472518662L, st_mtime=1469435178L, st_ctime=1472518662L)
 6 >>> metadata.st_size
 7 4934265L
 8 >>> import humansize
 9 >>> humansize.approximate_size(metadata.st_size )
10 ‘4.0 MiB‘
11 >>>