tail

[Avi Gross]

This seems to be a regular refrain where someone wants something as STANDARD in a programming language or environment and others want to keep it lean and mean or do not see THIS suggestion as particularly important or useful.
Looking at the end of something is extremely common. Packages like numpy/pandas in Python often provide functions with names like head or tail as do other languages where data structures with names like data.frame are commonly used. These structures are in some way indexed to make it easy to jump towards the end. Text files are not.

Efficiency aside, a 3-year-old (well, certainly a 30 year old)  can cobble together a function that takes a filename assumed to be textual and reads the file into some data structure that stores the lines of the file and so it can be indexed by line number and also report the index of the final line. The data structure can be a list of lists or a dictionary with line numbers as keys or a numpy ...

So the need for this functionality seems obvious but then what about someone who wants a bunch of random lines from a file? Need we satisfy their wish to pick random offsets from the file and get the line in which the offset is in middle of or the one about to start? Would that even be random if line lengths vary? Text files were never designed to be used efficiently except for reading and writing and certainly not for something like sorting.

Again, generally you can read in the darn file and perform the operation and free up whatever memory you do  not need. If you have huge files, fine, but then why make a special function be part of the default setup if it is rarely used? Why not put it in a module/package called BigFileBatches alongside other functions useful to do things in batches? Call that when needed but for smaller files, KISS.


-----Original Message-----
From: Dennis Lee Bieber <wlfraed at ix.netcom.com>
To: python-list at python.org
Sent: Wed, May 11, 2022 6:15 pm
Subject: Re: tail

On Thu, 12 May 2022 06:07:18 +1000, Chris Angelico <rosuav at gmail.com>
declaimed the following:

>I don't understand why this wants to be in the standard library.
>
    Especially as any Linux distribution probably includes the compiled
"tail" command, so this would only be of use on Windows.

    Under recent Windows, one has an equivalent to "tail" IFF using
PowerShell rather than the "DOS" shell.

https://www.middlewareinventory.com/blog/powershell-tail-file-windows-tail-command/

or install a Windows binary equivalent http://tailforwin32.sourceforge.net/


-- 
    Wulfraed                Dennis Lee Bieber        AF6VN
    wlfraed at ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/
-- 
https://mail.python.org/mailman/listinfo/python-list