Underscores in Python numbers

[Gustav Hållberg]

I tried finding a discussion around adding the possibility to have
optional underscores inside numbers in Python. This is a popular option
available in several "competing" scripting langauges, that I would love
to see in Python.

Examples:
1_234_567
0xdead_beef
3.141_592

Would appreciate if someone could find a pointer to a previous
discussion on this topic, or add it to a Python-feature-wishlist.

- Gustav

[Devan L]

Re: Underscores in Python numbers

Gustav Hållberg wrote:[color=blue]
> I tried finding a discussion around adding the possibility to have
> optional underscores inside numbers in Python. This is a popular option
> available in several "competing" scripting langauges, that I would love
> to see in Python.
>
> Examples:
> 1_234_567
> 0xdead_beef
> 3.141_592
>
> Would appreciate if someone could find a pointer to a previous
> discussion on this topic, or add it to a Python-feature-wishlist.
>
> - Gustav[/color]

I'm not sure what the _s are for, but I'm guessing they serve as
separators ("." or "," depending on where you're from). I think the _s
look ugly to me, besides, underscores look more like spaces than
separators.

[Peter Hansen]

Re: Underscores in Python numbers

Gustav Hållberg wrote:[color=blue]
> I tried finding a discussion around adding the possibility to have
> optional underscores inside numbers in Python. This is a popular option
> available in several "competing" scripting langauges, that I would love
> to see in Python.
>
> Examples:
> 1_234_567
> 0xdead_beef
> 3.141_592
>
> Would appreciate if someone could find a pointer to a previous
> discussion on this topic, or add it to a Python-feature-wishlist.[/color]

Perhaps these threads, via Google?

http://groups.google.com/group/comp.lang.python/search?group=comp.lang.python&q=numeric+literals+underscores

-Peter

[Dave Hansen]

Re: Underscores in Python numbers

On 7 Nov 2005 18:02:09 -0800 in comp.lang.pytho n, "Gustav Hållberg"
<gustav@gmail.c om> wrote:
[color=blue]
>I tried finding a discussion around adding the possibility to have
>optional underscores inside numbers in Python. This is a popular option
>available in several "competing" scripting langauges, that I would love
>to see in Python.
>
>Examples:
> 1_234_567
> 0xdead_beef
> 3.141_592
>
>Would appreciate if someone could find a pointer to a previous
>discussion on this topic, or add it to a Python-feature-wishlist.[/color]

I've never needed them in Python, but I've very often wished for them
in C. Along with 0b(0|1)* for binary numbers, where they'd be even
more useful.

Of course, I write _far_ more code in C than Python. But I've seen
enough bugs of the sort where someone wrote 1200000 when they meant
12000000, that I see great value in being able to specify 12_000_000.

Regards,
-=Dave

--
Change is inevitable, progress is not.

[Roy Smith]

Re: Underscores in Python numbers

Dave Hansen <iddw@hotmail.c om> wrote:[color=blue]
> Of course, I write _far_ more code in C than Python. But I've seen
> enough bugs of the sort where someone wrote 1200000 when they meant
> 12000000, that I see great value in being able to specify 12_000_000.[/color]

I'll admit that being able to write 12_000_000 would be convenient.
On the other hand, writing 12 * 1000 * 1000 is almost as clear. In C,
the multiplication would be done at compile time, so it's not even any
less efficient. I'm not sure how Python handles that, but if it
turned out to be a serious run-time performance issue, it's easy
enough to factor it out into something that's done once and stored.

Bottom line, embedded no-op underscores in numbers would be nice (and,
IHMO, should be added), but the lack of such a feature should not be
used as an excuse to write such unreadable monstrosities as 12000000
in source code.

Semi-related: see Jakob Nielsen's complaint about having to enter
credit card numbers as 16-digit strings with no breaks on web forms
(http://www.useit.com/alertbox/designmistakes.html, item #7, last
bullet point).

[Dave Hansen]

Re: Underscores in Python numbers

Sorry for the delayed response. I somehow missed this earlier.

On Tue, 8 Nov 2005 15:39:09 +0000 (UTC) in comp.lang.pytho n,
roy@panix.com (Roy Smith) wrote:
[color=blue]
>Dave Hansen <iddw@hotmail.c om> wrote:[color=green]
>> Of course, I write _far_ more code in C than Python. But I've seen
>> enough bugs of the sort where someone wrote 1200000 when they meant[/color][/color]

Digression: 1 was enough.
[color=blue][color=green]
>> 12000000, that I see great value in being able to specify 12_000_000.[/color]
>
>I'll admit that being able to write 12_000_000 would be convenient.
>On the other hand, writing 12 * 1000 * 1000 is almost as clear. In C,[/color]

Perhaps, but it's pretty obvious that something's wrong when you have
to resort to ugly tricks like this to make the value of a simple
integer constant "clear."

And think about 64 (or longer) -bit unsigned long long hexadecimal
values. How much nicer is 0xFFF0_FF0F_F0F F_0FFF_ULL than
0xFFF0FF0FF0FF0 FFFULL? I guess we could do something like
((((0xFFF0ULL<< 16)|0xFF0FULL)< <16)|0xF0FFULL) <<16)|0x0FFFULL ), but I'm
not sure it's any better.

Regards,
-=Dave

--
Change is inevitable, progress is not.

[Dave Hansen]

Re: Underscores in Python numbers

Sorry for the delayed response. I somehow missed this earlier.

On Tue, 8 Nov 2005 15:39:09 +0000 (UTC) in comp.lang.pytho n,
roy@panix.com (Roy Smith) wrote:
[color=blue]
>Dave Hansen <iddw@hotmail.c om> wrote:[color=green]
>> Of course, I write _far_ more code in C than Python. But I've seen
>> enough bugs of the sort where someone wrote 1200000 when they meant[/color][/color]

Digression: 1 was enough.
[color=blue][color=green]
>> 12000000, that I see great value in being able to specify 12_000_000.[/color]
>
>I'll admit that being able to write 12_000_000 would be convenient.
>On the other hand, writing 12 * 1000 * 1000 is almost as clear. In C,[/color]

Perhaps, but it's pretty obvious that something's wrong when you have
to resort to ugly tricks like this to make the value of a simple
integer constant "clear."

And think about 64 (or longer) -bit unsigned long long hexadecimal
values. How much nicer is 0xFFF0_FF0F_F0F F_0FFF_ULL than
0xFFF0FF0FF0FF0 FFFULL? I guess we could do something like
((((0xFFF0ULL<< 16)|0xFF0FULL)< <16)|0xF0FFULL) <<16)|0x0FFFULL ), but I'm
not sure it's any better.

Regards,
-=Dave

--
Change is inevitable, progress is not.

[bonono@gmail.com]

Re: Underscores in Python numbers

Personally, I would rather see the int() and float() function be
smarter to take what is used for this, i.e. :

a = int("1,234,567" )

Of course, also support the locale variant where the meaning of "," and
"." is swapped in most European countries.

Gustav Hållberg wrote:[color=blue]
> I tried finding a discussion around adding the possibility to have
> optional underscores inside numbers in Python. This is a popular option
> available in several "competing" scripting langauges, that I would love
> to see in Python.
>
> Examples:
> 1_234_567
> 0xdead_beef
> 3.141_592
>
> Would appreciate if someone could find a pointer to a previous
> discussion on this topic, or add it to a Python-feature-wishlist.
>
> - Gustav[/color]

[bonono@gmail.com]

Re: Underscores in Python numbers

Personally, I would rather see the int() and float() function be
smarter to take what is used for this, i.e. :

a = int("1,234,567" )

Of course, also support the locale variant where the meaning of "," and
"." is swapped in most European countries.

Gustav Hållberg wrote:[color=blue]
> I tried finding a discussion around adding the possibility to have
> optional underscores inside numbers in Python. This is a popular option
> available in several "competing" scripting langauges, that I would love
> to see in Python.
>
> Examples:
> 1_234_567
> 0xdead_beef
> 3.141_592
>
> Would appreciate if someone could find a pointer to a previous
> discussion on this topic, or add it to a Python-feature-wishlist.
>
> - Gustav[/color]

[Steven D'Aprano]

Re: Underscores in Python numbers

On Fri, 18 Nov 2005 16:26:08 -0800, bonono@gmail.co m wrote:
[color=blue]
> Personally, I would rather see the int() and float() function be
> smarter to take what is used for this, i.e. :
>
> a = int("1,234,567" )[/color]

But the problem isn't just with conversion of strings. It is also
with literals.

n = 99999999999

Without counting, how many nines?

Obviously repeated digits is an extreme case, but even different digits
are easier to process if grouped. That's why we write phone numbers like
62 3 9621 2377 instead of 62396212377.

Here is a thought: Python already concatenates string literals:

"abc" "def" is the same as "abcdef".

Perhaps Python should concatenate numeric literals at compile time:

123 456 is the same as 123456.

Off the top of my head, I don't think this should break any older code,
because 123 456 is not currently legal in Python.


--
Steven.

[Steven D'Aprano]

Re: Underscores in Python numbers

On Fri, 18 Nov 2005 16:26:08 -0800, bonono@gmail.co m wrote:
[color=blue]
> Personally, I would rather see the int() and float() function be
> smarter to take what is used for this, i.e. :
>
> a = int("1,234,567" )[/color]

But the problem isn't just with conversion of strings. It is also
with literals.

n = 99999999999

Without counting, how many nines?

Obviously repeated digits is an extreme case, but even different digits
are easier to process if grouped. That's why we write phone numbers like
62 3 9621 2377 instead of 62396212377.

Here is a thought: Python already concatenates string literals:

"abc" "def" is the same as "abcdef".

Perhaps Python should concatenate numeric literals at compile time:

123 456 is the same as 123456.

Off the top of my head, I don't think this should break any older code,
because 123 456 is not currently legal in Python.


--
Steven.

[bonono@gmail.com]

Re: Underscores in Python numbers


Steven D'Aprano wrote:[color=blue]
> On Fri, 18 Nov 2005 16:26:08 -0800, bonono@gmail.co m wrote:
>[color=green]
> > Personally, I would rather see the int() and float() function be
> > smarter to take what is used for this, i.e. :
> >
> > a = int("1,234,567" )[/color]
>
> But the problem isn't just with conversion of strings. It is also
> with literals.
>
> n = 99999999999
>
> Without counting, how many nines?[/color]
For readability, I don't see why it cannot be written as :

n = int("99,999,999 ,999")

we already needs to do this for decimal("9.9")

[bonono@gmail.com]

Re: Underscores in Python numbers


Steven D'Aprano wrote:[color=blue]
> On Fri, 18 Nov 2005 16:26:08 -0800, bonono@gmail.co m wrote:
>[color=green]
> > Personally, I would rather see the int() and float() function be
> > smarter to take what is used for this, i.e. :
> >
> > a = int("1,234,567" )[/color]
>
> But the problem isn't just with conversion of strings. It is also
> with literals.
>
> n = 99999999999
>
> Without counting, how many nines?[/color]
For readability, I don't see why it cannot be written as :

n = int("99,999,999 ,999")

we already needs to do this for decimal("9.9")

[Stefan Rank]

Re: Underscores in Python numbers

on 19.11.2005 06:56 Steven D'Aprano said the following:
[snip][color=blue]
>
> Perhaps Python should concatenate numeric literals at compile time:
>
> 123 456 is the same as 123456.
>
> Off the top of my head, I don't think this should break any older code,
> because 123 456 is not currently legal in Python.[/color]

+1

but only allow (a single ?) space(s), otherwise readability issues ensue.

The other idea of teaching int() about separator characters has
internationalis/zation issues:
In many European countries, one would naturally try::

int('500.000,23 ')

instead of::

int('500,000.23 ')

--
stefan

[Stefan Rank]

Re: Underscores in Python numbers

on 19.11.2005 06:56 Steven D'Aprano said the following:
[snip][color=blue]
>
> Perhaps Python should concatenate numeric literals at compile time:
>
> 123 456 is the same as 123456.
>
> Off the top of my head, I don't think this should break any older code,
> because 123 456 is not currently legal in Python.[/color]

+1

but only allow (a single ?) space(s), otherwise readability issues ensue.

The other idea of teaching int() about separator characters has
internationalis/zation issues:
In many European countries, one would naturally try::

int('500.000,23 ')

instead of::

int('500,000.23 ')

--
stefan