Things that won't change in Python

A lengthy and strongly opinionated post about Python features to the python-ideas mailing list garnered various responses there, from some agreement to strong disagreement to calling it "trolling", but it may also lead the Python community to better define what Python is. Trolling seems a somewhat unfair characterization, but Simon Lovell's "Python Reviewed" post did call out some of the fundamental attributes of the language and made some value judgments that were seen as either coming from ignorance of the language or simply as opinions that were stated as facts in a brusque way. The thread eventually led to the creation of a document meant to help head off this kind of thread in the future.

Good, bad, and ugly

Lovell's message started off with a short list of "The Good", but quickly moved into a list of "The Bad" that included more explanation of the features he disliked. It included entries for things he was unhappy with: the colons at the end of if, for, and similar statements (which he deemed unnecessary), the lack of an end statement for blocks (less readable), and no do-while loop. He also thought that the else clause for loops should have a different name (and suggested whenFalse), that print() should not have been changed to a function in Python 3 ("adds no positive value that I can see"), etc. As might be guessed, he ended with an entry for "The Ugly". It complained about non-zero integer values being treated as "true" ("crapulence from C" that violates the "explicit is better than implicit" principle from PEP 20).

Some of the entries in the good and bad lists were either incorrect or misunderstandings of how to use Python, which put Lovell on the wrong foot with many python-ideas readers. But his tone also put some off. As Stephen D'Aprano put it: "As a newcomer to this community, and apparently the language as well, do you understand how obnoxious and arrogant it comes across for you to declare what is and isn't 'good' and 'bad' about the language [...]". He warned Lovell that the tone of his message might make responses "blunt or even brusque", but he did reply at some length.

For example, D'Aprano pointed him at the FAQ entry that explains the reasons behind the colons for if, et al. (readability, essentially). He also disagreed strongly with the need for an end statement, but agreed that else for loops was misnamed (though it is too late to change that now). Meanwhile, D'Aprano said that he preferred treating non-zero numbers as true values.

Chris Angelico also thought that the way Python does truth testing is both helpful and non-ugly:

D'Aprano and Angelico both agreed with the decision to change print() to a function. Angelico said that it "adds heaps of positive value to a lot of people", while D'Aprano was more specific about the advantages:

Overall, the thread proceeded like most in Python mailing lists. Folks were generally helpful even when they were resolute about disagreeing with Lovell. On the other hand, Lovell didn't seem to quite pick up the vibe of the list. For example, responses like "I don't really see how that can be argued" or "I may be arrogant but I can't take it seriously" did not go over all that well.

Trolling?

Eventually, Guido van Rossum started a new thread entitled "How to respond to trolling". In it, he suggested that responding to Lovell's posts was counterproductive: "I think a much more effective response would have been a resounding silence." But several thought that was not entirely fair. Ned Batchelder said:

There were a number of suggestions in the original thread for Lovell to take the topic to a different mailing list (python-list, which is for more general Python discussions). Since Lovell wasn't really suggesting changes to the language (at least formally), some thought the discussion belonged on a different list. Though Nick Timkovich wasn't sure that even if Lovell had proposed the changes it would be a topic for python-ideas: "If you're proposing throwing half of Python's current syntax in the bin, this isn't the right list either."

However Van Rossum was adamant that the Lovell's post did not deserve a response:

But D'Aprano saw things differently. What Van Rossum had suggested was effectively "shunning" Lovell, which is "a particularly nasty form of passive-aggression, as the person being shunned doesn't even get any hint as to what they have done to bring it on". He also pointed out that it may not have been clear to Lovell that he was crossing a line, because it is an unwritten one:

Things that won't change

In an attempt to rectify the "undocumented" piece, D'Aprano proposed an informational PEP called "Things that won't change in Python". In it, he listed a number of things that are known to be immutable in Python, but that perhaps those outside the community are not aware of. The rationale, as described in the PEP, is to reduce noise on python-ideas and other lists by heading off suggestions that have no chance to be accepted "because the benefit is too little, the cost of changing the language (including backwards compatibility) is too high, or simply because it goes against the design preferred by the BDFL".

Some of the things listed in the PEP are fairly obvious (Python 3 will not be abandoned, there will be no Python 2.8), some were at least partly in response to Lovell's post (colons after if and the like, no end statement, print() will remain a function), and others came from recurring suggestions to the lists (no braces around blocks, significant indentation will remain, the >>> interactive prompt will stay as the default). Each entry comes with a bit of justification, often with links to a FAQ entry or other documentation.

In general the response was positive. There was naturally some wordsmithing (or bikeshedding) over the name and whether it should be a PEP or something else, but there was little disagreement over the listed choices—unsurprisingly. Van Rossum said that he had not followed the discussion closely, but that it made sense to delineate some unchangeable features of the language:

Lovell did reply to Van Rossum's "trolling" message, but was still on the offensive ("More than half of what I suggested could have and should be implemented."). He also continued to insist that Python's "truthiness" is ugly: "Calling truthiness of non boolean data 'Ugly' is an insult? It is ugly." Brett Cannon, who is one of the list administrators, tried one more time to explain why Lovell was not getting the response he was seemingly looking for:

That led to a bit of a digression on the term "warts", which is sometimes used in the Python community to describe some missteps and misfeatures that exist in the language. It was mostly agreed that warts are "ugly" at some level, but it is a self-applied term, which makes it a bit more acceptable. And Van Rossum is not even sure they are missteps, exactly:

In the end, the situation was handled pretty well, as is always the case in the Python community, it seems. One can imagine a much ruder response that a critical post like that might receive in other free-software communities. So far, it doesn't seem like the PEP has gone anywhere since it was discussed in mid-January, but the exercise and discussion were useful; if nothing else it can serve as a place to point the next person who comes along with "great ideas" that will never become a part of Python.