[0..9] list (range) syntax

[Michal Bozon]

many Python newcomers are confused why
range(10), does not include 10.

If there was a proposal for the new
syntax for ranges, which is known
e.g. from Pascal or Ruby...

>>[0..10]

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

....is there a chance to be approved ?

We have had a short discussion on it
at the irc, I hope that the fact
that nobody agreed it is a good idea
was just an accident :)

-m.

PS:
to dream further..

>>(0..10)

<generator object at 0xb7618dac>

or

>>(0..10)

(0..10)

or

>>(0..10)

range(0, 11)

[mensanator]

On Oct 24, 5:44 pm, Michal Bozon <[e-mail]:

many Python newcomers are confused why
range(10), does not include 10.

How can they be confused?

Does base 10 have a digit ten?
Does base 2 have a digit two?
Does base 16 have a digit sixteen?

Haven't you stopped counting on your fingers when
you leave grade school?

>
If there was a proposal for the new
syntax for ranges, which is known
e.g. from Pascal or Ruby...

>[0..10]

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

...is there a chance to be approved ?

"These go to 11."

>
We have had a short discussion on it
at the irc, I hope that the fact
that nobody agreed it is a good idea
was just an accident :)

Wait a minute...comp.lang.python. I must have
accidentally gotten into the wrong newsgroup.

>
-m.

PS:
to dream further..

>(0..10)

<generator object at 0xb7618dac>

or

>(0..10)

(0..10)

or

>(0..10)

range(0, 11)

[Steven D'Aprano]

On Wed, 24 Oct 2007 16:28:20 -0700, me********@aol.com wrote:

On Oct 24, 5:44 pm, Michal Bozon <[e-mail]:

>many Python newcomers are confused why range(10), does not include 10.

How can they be confused?

Because in common English, counting starts at 1 and ranges normally
include both end points (that is, it is a "closed" interval). If you say
"I'll be away from the 4th to the 7th" and then turn up on the 7th,
nearly everyone will wonder why you're back a day early.

Does base 10 have a digit ten?
Does base 2 have a digit two?
Does base 16 have a digit sixteen?

Haven't you stopped counting on your fingers when you leave grade
school?

range(N) is not designed to return the digits used in base N strings, and
any connection is weak (what base does range(3, 25, 4) correspond to?).
What little correspondence there is is an accidental coincidence of how
we write numbers, not a fundamental fact about half-open intervals like
range().

Having said that, and regardless of common English usage, using half-open
intervals almost always leads to simpler programming and fewer errors.
Creating syntax support for beginners to make extra off-by-one bugs is a
terrible idea, no matter how seductive it seems for newbies. I know Ruby
has (to my mind confusing!) support for both closed and half-open
intervals, but I wonder how useful it is in practice?

Ruby expression =Python equivalent

1..5 =range(1, 6)
1...5 =range(1, 5)

--
Steven.

[Carl Banks]

On Oct 24, 6:44 pm, Michal Bozon <[e-mail]:

many Python newcomers are confused why
range(10), does not include 10.

If there was a proposal for the new
syntax for ranges, which is known
e.g. from Pascal or Ruby...

>[0..10]

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

...is there a chance to be approved ?

We have had a short discussion on it
at the irc, I hope that the fact
that nobody agreed it is a good idea
was just an accident :)

No, sorry, it's just not going to happen.

In fact, the opposite is happening. Python is removing the few cases
that use a closed interval. For example, random.randint(a,b), which
returned a random integer in range a to b inclusive, was deprecated in
favor of random.randrange(a,b), which generates a random integer in
range a to b, not inclusive.
The advantages of open ranges are especially apparent to someone like
me, who uses Python at home, then has to go to work and Matlab. It's
not that I accidentally use open intervals a lot (I've gotten into the
habit of making sure I am using closed intervals whenever my tension
level is high :), but all the extra "+1"s and "-1"s that I need when
splicing arrays gets pretty old.
Carl Banks

[Wildemar Wildenburger]

Michal Bozon wrote:

The .. syntax was not meant only as something
which would include the last item,
but also/rather a range list syntactic shortcut:

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] -->
[0, 1, ... 9, 10] -->
[0..10]

OK, I see.

But I still fail to see where this is useful. All these 3 statements
create a list from 0 to 10 including.

If, however, the ".." operator would recognize patterns before and after
itself, I could see your point (e.g. [0, 1, 2, 4, 8, .. 128, 256, 512]).
Buts thats pretty academic, maybe good for a specialized computation
language.

And I feel that my "write a function" argument still holds.

/W