[Python-ideas] Python Users Aren't Perfect

Ned Batchelder ned at nedbatchelder.com
Mon Dec 12 14:15:45 CET 2011

On 12/12/2011 8:07 AM, Antoine Pitrou wrote:
> On Mon, 12 Dec 2011 08:00:28 -0500
> Ned Batchelder<ned at nedbatchelder.com>
> wrote:
>> On 12/10/2011 9:42 AM, Oleg Broytman wrote:
>>> On Sat, Dec 10, 2011 at 02:16:21PM +0000, Richard Prosser wrote:
>>>> Although I love Python there are some aspects of the language design which
>>>> are disappointing and which can even lead to problems in some cases.
>>>      What really is disappointing is the number of people who criticize
>>> Python without knowing it.
>>>> Another awkward 'feature' is the requirement for a trailing comma in
>>>> singleton tuples, due I believe to the use of expression parentheses rather
>>>> than (say) the use of special brackets like chevrons.
>>>      You do not understand the syntax. Parens do not construct tuples -
>>> commas do. So for every tuple - even of length 1 - you must have a
>>> comma. The only exception is an empty tuple (of length 0).
>> I don't think we have to go as far as blaming the user.  Tuple syntax is
>> a little tricky, people often trip up on (x,) as a single-item tuple.
>> You and I understand why it is, and there isn't a better alternative,
>> but that one-item syntax sticks out when compared to the others: (), (x,
>> y), (x, y, z), etc.  This is a true "gotcha" as Richard originally
>> expressed it.
> I think it would be more of a gotcha if parentheses were enough to
> create a tuple, though. Parentheses are useful to group operations,
> either for stylistic / syntactic support (think multi-line statements),
> or to work around operator precedence. Creating a tuple by mistake
> because you put some parentheses where not necessary would be really
> annoying.
Believe me, I understand the issues.  It is true, though that the 
single-element tuple syntax is often a surprise to people, and often 
well into their Python learning experience.  We often repeat, "it isn't 
parens that make a tuple, but a comma."  Then why when displaying a 
tuple does Python insist on using parens around it?

 >>> 1, 2, 3
     (1, 2, 3)

I'm not saying it shouldn't, it's a rhetorical question.  The repr of a 
tuple always includes parens, even though "parens don't make a tuple."  
It's the best of all the options, but let's face it: it's confusing.

> Regards
> Antoine.
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