Python初体验-开篇 代码全析

            第一次接触Python，现在就开始蟒蛇的威力。

 

            一、首先贴上我们要解析的code:  下载代码

                         '''Convert file sizes to human-readable form. Available functions: approximate_size(size, a_kilobyte_is_1024_bytes) takes a file size and returns a human-readable string Examples: >>> approximate_size(1024) '1.0 KiB' >>> approximate_size(1000, False) '1.0 KB' ''' SUFFIXES = {1000: ['KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'], 1024: ['KiB', 'MiB', 'GiB', 'TiB', 'PiB', 'EiB', 'ZiB', 'YiB']} def approximate_size(size, a_kilobyte_is_1024_bytes=True): '''Convert a file size to human-readable form. Keyword arguments: size -- file size in bytes a_kilobyte_is_1024_bytes -- if True (default), use multiples of 1024 if False, use multiples of 1000 Returns: string ''' if size < 0: raise ValueError('number must be non-negative') multiple = 1024 if a_kilobyte_is_1024_bytes else 1000 for suffix in SUFFIXES[multiple]: size /= multiple if size < multiple: return '{0:.1f} {1}'.format(size, suffix) raise ValueError('number too large') if __name__ == '__main__': print(approximate_size(1000000000000, False)) print(approximate_size(1000000000000)) # Copyright (c) 2009, Mark Pilgrim, All rights reserved. # # Redistribution and use in source and binary forms, with or without modification, # are permitted provided that the following conditions are met: # # * Redistributions of source code must retain the above copyright notice, # this list of conditions and the following disclaimer. # * Redistributions in binary form must reproduce the above copyright notice, # this list of conditions and the following disclaimer in the documentation # and/or other materials provided with the distribution. # # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS' # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE # ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE # LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS # INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE # 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

                        

 

         二、看看我们代码的执行情况：

    

                    

                   

                    我的系统里装了Cygwin，该软件能够模拟linux系统里的shell。

             首先， 使用ls命令查看当前目录里包含的文件，发现该程序的代码文件humansize.py;

             第二， 使用python命令执行该程序，注意加上文件扩展名，否则出现如图所示的NameError

         错误；执行成功后，可以看见输出（对10的12次方字节做单位转换）：第一行为以1000进制做的

         单位转换，第二行以1024进制做的单位转换。

              if __name__ == '__main__': print(approximate_size(1000000000000, False)) print(approximate_size(1000000000000))

 

 

       三、再看看代码在Python Shell的调用情况：