python-peps/pep-0666.txt

PEP: 666
Title: Reject Foolish Indentation
Version: $Revision$
Last-Modified: $Date$
Author: lac@strakt.com (Laura Creighton)
Status: Rejected
Type: Standards Track
Content-Type: text/x-rst
Created: 03-Dec-2001
Python-Version: 2.2
Post-History: 5-Dec-2001


Abstract
========

Everybody agrees that mixing tabs and spaces is a bad idea.  Some
people want more than this.  I propose that we let people define
whatever Python behaviour they want, so it will only run the way
they like it, and will not run the way they don't like it.  We
will do this with a command line switch.  Programs that aren't
formatted the way the programmer wants things will raise
``IndentationError``.

- ``python -TNone`` will refuse to run when there are any tabs.
- ``python -Tn`` will refuse to run when tabs are not exactly ``n`` spaces
- ``python -TOnly`` will refuse to run when blocks are indented by anything
  other than tabs

People who mix tabs and spaces, naturally, will find that their
programs do not run.  Alas, we haven't found a way to give them an
electric shock as from a cattle prod remotely.  (Though if somebody
finds out a way to do this, I will be pleased to add this option to
the PEP.)


Rationale
=========

Python-list@python.org (a.k.a. comp.lang.python) is periodically
awash with discussions about tabs and spaces.  This is inevitable,
given that indentation is syntactically significant in Python.
This has never solved anything, and just makes various people
frustrated and angry.  Eventually they start saying rude things to
each other which is sad for all of us.  And it is also sad that
they are wasting their valuable time which they could spend
creating something with Python.  Moreover, for the Python community
as a whole, from a public relations point of view, this is quite
unfortunate.  The people who aren't posting about tabs and spaces,
are, (unsurprisingly) invisible, while the people who are posting
make the rest of us look somewhat foolish.

The problem is that there is no polite way to say 'Stop wasting
your valuable time and mine.'  People who are already in the middle
of a flame war are not well disposed to believe that you are acting
out of compassion for them, and quite rightly insist that their own
time is their own to do with as they please.  They are stuck like
flies in treacle in this wretched argument, and it is self-evident
that they cannot disengage or they would have already done so.

But today I had to spend time cleaning my keyboard because the 'n'
key is sticking.  So, in addition to feeling compassion for these
people, I am pretty annoyed.  I figure if I make this PEP, we can
then ask Guido to quickly reject it, and then when this argument
next starts up again, we can say 'Guido isn't changing things to
suit the tab-haters or the only-tabbers, so this conversation is a
waste of time.'  Then everybody can quietly believe that a) they
are correct and b) other people are fools and c) they are
undeniably fortunate to not have to share a lab with idiots, (which
is something the arguers could do _now_, but apparently have
forgotten).

And python-list can go back to worrying if it is too smug, rather
than whether it is too hostile for newcomers.  Possibly somebody
could get around to explaining to me what is the difference between
``__getattr__`` and ``__getattribute__`` in non-Classic classes in 2.2, a
question I have foolishly posted in the middle of the current tab
thread.  I would like to know the answer to that question [1]_.

This proposal, if accepted, will probably mean a heck of a lot of
work for somebody.  But since I don't want it accepted, I don't
care.


References
==========

.. [1] Tim Peters already has (private correspondence).  My early 2.2
       didn't have a ``__getattribute__``, and ``__getattr__`` was
       implemented like ``__getattribute__`` now is.  This has been
       fixed.  The important conclusion is that my Decorator Pattern
       is safe and all is right with the world.


Copyright
=========

This document has been placed in the public domain.



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