[Python-Dev] PEP dircache.py core modification

[Palisade]

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This is my first exposure to the Python language, and I have found many things
to my liking. I have also noticed some quirks which I regard as assumption
flaws on part of the interpreter. The one I am interested in at the moment is
the assumption that we should leave the . and .. directory entries out of the
directory listing returned by os.listdir().

I have read the PEP specification and have thereby prepared a PEP for your
perusal. I hope you agree with me that this is both a philosophical issue
based in tradition as well as a duplication of effort problem that can be
readily solved with regards to backwards compatibility.

Thank you.

I have attached the PEP to this message.

Sincerely,
Nelson Rush

"This most beautiful system [The Universe] could only proceed from the
dominion of an intelligent and powerful Being."
-- Sir Isaac Newton

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PEP: 
Title: os.listdir Full Directory Listing
Version: 
Author: palisade@users.sourceforge.net (Nelson Rush)
Status: 
Type: 
Created: 16/3/2001
Post-History: 

Introduction

    This PEP explains the need for two missing elements in the list returned
    by the os.listdir function.



Proposal

    It is obvious that having os.listdir() return a list with . and .. is
    going to cause many existing programs to function incorrectly. One
    solution to this problem could be to create a new function os.listdirall()
    or os.ldir() which returns every file and directory including the . and ..
    directory entries. Another solution could be to overload os.listdir's
    parameters, but that would unnecessarily complicate things.



Key Differences with the Existing Protocol

    The existing os.listdir() leaves out both the . and .. directory entries
    which are a part of the directory listing as is every other file.



Examples

    import os
    dir = os.ldir('/')
    for i in dir:
        print i

    The output would become:

    .
    ..
    lost+found
    tmp
    usr
    var
    WinNT
    dev
    bin
    home
    mnt
    sbin
    boot
    root
    man
    lib
    cdrom
    proc
    etc
    info
    pub
    .bash_history
    service



Dissenting Opinion

    During a discussion on Efnet #python, an objection was made to the
    usefulness of this implementation. Namely, that it is little extra
    effort to just insert these two directory entries into the list.

    Example:

    os.listdir() + ['.','..']

    An argument can be made however that the inclusion of both . and ..
    meet the standard way of listing files within directories. It is on
    basis of this common method between languages of listing directories
    that this tradition should be maintained.

    It was also suggested that not having . and .. returned in the list
    by default is required to be able to perform such actions as `cp * dest`.

    However, programs like `ls` and `cp` list and copy files excluding
    any directory that begins with a period. Therefore there is no need
    to clip . and .. from the directory list by default. Since anything
    beginning with a period is considered to be hidden.



Reference Implementation

    The reference implementation of the new dircache.py core ldir function
    extends listdir's functionality as proposed.

    http://palisade.rm-f.net/dircache.py



Copyright

    This document has been placed in the Public Domain.

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