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How the Python oldfiles script works

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See the Python source file, oldfiles, for the actual Python code. Here is a general description of the program's operation:

  1. The script starts by importing the sys and os modules from the standard Python library, containing many useful systems programming functions.
  2. We also import our pathinfo module so we can use our PathInfo object (see ` A Python file info object') to represent information about files.
  3. We then define a new class called Old, which is basically a slightly modified PathInfo object. It replaces that object's built-in __cmp__ method with a new method that causes Old objects to sort so that ones for the largest files sort first. We also replace the __str__ method, to change the way that these objects are output by a print statement.
  4. In the main program sequence, the Python function os.walk() is used to visit every directory and file. The function Visitor() is called by os.walk() once for each pathname in the directory tree, and it creates a Old object for that pathname. Each Old object is appended to a global list named files.
  5. The files list is sorted using the list type's built-in .sort() method. This orders the Old objects from largest to smallest file size.
  6. A for loop prints each Old object in the files list.

See also: oldfiles: Where are my oldest files?
Previous: How to run the Python oldfiles script
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John Shipman,
Last updated: 2004/03/07 01:41:15 UT
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