"Don't rebind built-in names*" - it confuses readers

[Rick Johnson]

On Monday, June 10, 2013 9:56:43 PM UTC-5, Steven D'Aprano wrote:
> On Mon, 10 Jun 2013 20:14:55 -0400, Terry Jan Reedy wrote:
> > For instance, open Lib/idlelib/GrepDialog.py in an editor that colorizes
> > Python syntax, such as Idle's editor, jump down to the bottom and read
> > up, and (until it is patched) find
> >                      list.append(fn)
> > with 'list' colored as a builtin. Stop. That looks wrong. List.append
> > needs two arguments: a list instance and an object to append to the
> > list. The 'solution' is in a previous line
> >          list = []
> > Reading further, one sees that the function works with two lists, a list
> > of file names, unfortunately called 'list', and a list of
> > subdirectories, more sensibly call 'subdirs'. 
> Yes, that is a poor choice of names. But sometimes you are
> dealing with a generic list, and calling it "filenames"
> would be equally inappropriate :-)

I agree, however hopefully you're joking, because in the past you've argued that programmers should never use variables as generic as "list", "string", "integer", "float", etc... even though there are instances when all you need to know is what type your working with.

> > I was initially confused
> > and reading the code still takes a small bit of extra mental energy.
> > Idle stays confused and will wrongly color the list instance name until
> > it is changed. Calling the file list 'fnames' or 'filenames' would have
> > been clearer to both me and Idle.
> Correct. The downside of editors that colourise text is
> that sometimes they colourise it wrong. 

One of the most important side-effects of using an editor with colorizing capabilities is to show you that you're using a built-in or keyword as a variable! I love when people comment on subjects they have no direct experience with, like for instance, you commenting on colonizers or GUI's -- LOL!

> In this case, how is the editor supposed to know that list
> no longer refers to the built-in list? 

Colonizers should ALWAYS colorize built-in (as built-in symbols) symbols EXCEPT when that symbol is part of a string or comment. 

> This is yet another good argument for being cautious about
> shadowing built- ins.

In a language designed like Python, yes. Unfortunately Python not only decided to expose built-in functions for constructing types instead of class identifiers, they also stole the best generic names! 

Sometimes all you need to know is the type of an object, not what it contains. I remember someone *cough-steven* talking about duck typing and how great it was to just treat a duck like a duck. Well, here we find ourselves treating a list like a list and your taking the opposite argument... why am i not surprised?

PS: Is that "D" in last name short for "DevilsAdvocate"? Steven "DevilsAdvocate" Prano.