A funnily inconsistent behavior of int and float

**Grant Edwards** · Apr 6 '08, 07:05 PM

Re: A funnily inconsistent behavior of int and float

On 2008-04-06, Lie <Lie.1296@gmail .comwrote:

I've noticed some oddly inconsistent behavior with int and float:
>
Python 2.5.1 (r251:54863, Mar 7 2008, 03:39:23)
[GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2

>>>int('- 345')

-345
>
works,

IMO, it oughtn't.

>>>float('- 345.083')

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for float(): - 345.083

That's the behavior I'd expect.

The problem seems to be that float can't accept spaces between
the sign and the number while int can. Possibly caused by some
missing regex statement. Minor and harmless (most of the
time), but should be made known.

--
Grant Edwards grante Yow! ... I live in a
at FUR-LINE FALLOUT SHELTER
visi.com

**Colin J. Williams** · Apr 6 '08, 09:05 PM

Re: A funnily inconsistent behavior of int and float

Grant Edwards wrote:

On 2008-04-06, Lie <Lie.1296@gmail .comwrote:
>

>I've noticed some oddly inconsistent behavior with int and float:
>>
>Python 2.5.1 (r251:54863, Mar 7 2008, 03:39:23)
>[GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2

>>>>int('- 345')

>-345
>>
>works,

>
IMO, it oughtn't.

Agreed it seems inconsistent with the
integer literal syntax
Python 2.5 Docs: 2.4.4 Integer and long
integer literals
Python 3.0 doesn't appear to spell out
the literal syntax.
It would be helpful if it did.

Colin W.

[snip]

**Mark Dickinson** · Apr 6 '08, 10:15 PM

Re: A funnily inconsistent behavior of int and float

On Apr 6, 1:29 pm, Lie <Lie.1...@gmail .comwrote:

I've noticed some oddly inconsistent behavior with int and float:
>
Python 2.5.1 (r251:54863, Mar 7 2008, 03:39:23)
[GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2>>int('- 345')
>
-345
>
works, but
>

>float('- 345.083')

>
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for float(): - 345.083

This is a known issue, that has been fixed for Python 3.0.
It was decided not to risk breakage by changing this in
Python 2.x. See:

Issue 1779: int("- 1") is valud, but float("- 1") isn't. Which is right? - Python tracker

http://bugs.python.org/issue1779

Mark

**Mark Dickinson** · Apr 7 '08, 07:55 PM

Re: A funnily inconsistent behavior of int and float

On Apr 7, 3:15 pm, "Terry Reedy" <tjre...@udel.e duwrote:

>
My suggestions:
1. Change signature to: int([number | string[, radix]).
This makes it clear that radix can only follow a string without having to
say so in the text.
>
2. Replace text with:
Convert a number or string to an integer. If no arguments are given,
return 0. If a number is given, return number.__int__( ). Conversion of
floating point numbers to integers truncates towards zero. A string must
be a base-radix integer literal optionally preceded by '+' or '-' (with no
space in between) and optionally surrounded by whitespace. A base-n
literal consists of the digits 0 to n-1, with 'a' to 'z' (or 'A' to 'Z')
having values 10 to 35. The default radix is 10. The allowed values are 0
and 2-36, with 0 the same as 10.
>
If 0 is not the same as 10, the last would have to be changed, but I could
not detect any difference in a quick test.
>
After looking at any comments here, I will consider submitting these to the
tracker.
>
Terry Jan Reedy

Looks good! The description should probably also mention the optional
'0b', '0o' or '0x' (or '0B', '0O', '0X') allowed between the sign and
the digits (or before the digits in the case of a missing sign) when
base=2, base=8 or base=16.

The only base 0 versus base 10 difference I could find was the
following:

>>int('033', 0)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 0: '033'
[38720 refs]

>>int('033')

33

Mark

**Mark Dickinson** · Apr 7 '08, 08:05 PM

Re: A funnily inconsistent behavior of int and float

On Apr 7, 3:53 pm, Mark Dickinson <dicki...@gmail .comwrote:

The only base 0 versus base 10 difference I could find was the
following:
>

>int('033', 0)

>
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 0: '033'
[38720 refs]>>int('033')
>
33
>
Mark

And also things like:

>>int('0x33')

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '0x33'
[38719 refs]

>>int('0x33', 0)

51
[38719 refs]

Mark

**Terry Reedy** · Apr 7 '08, 09:05 PM

Re: A funnily inconsistent behavior of int and float

"Mark Dickinson" <dickinsm@gmail .comwrote in message
news:1255ee3e-cc1e-4ae8-96f3-5f942c389c49@t5 4g2000hsg.googl egroups.com...

Thank you for the corrections. Here is my revised proposal:

int([number | string[, radix])
Convert a number or string to an integer. If no arguments are given,
return 0. If a number is given, return number.__int__( ). Conversion of
floating point numbers to integers truncates towards zero. A string must
be a base-radix integer literal optionally preceded by '+' or '-' (with no
space in between) and optionally surrounded by whitespace. A base-n
literal consists of the digits 0 to n-1, with 'a' to 'z' (or 'A' to 'Z')
having values 10 to 35. The default radix is 10. The allowed values are 0
and 2-36. Base-2, -8, and -16 literals can be optionally prefixed with
0b/0B, 0o/0O, or 0x/0X, as with integer literals in code. Radix 0 means to
interpret exactly as a code literal, so that the actual radix is 2, 8, 10,
or 16, and so that int('010',0) is not legal, while int('010') is.

Terry Jan Reedy

**Lie** · Apr 7 '08, 09:05 PM

Re: A funnily inconsistent behavior of int and float

On Apr 8, 2:15 am, "Terry Reedy" <tjre...@udel.e duwrote:
(snip)

2. Replace text with:
Convert a number or string to an integer. If no arguments are given,
return 0. If a number is given, return number.__int__( ). Conversion of
floating point numbers to integers truncates towards zero. A string must
be a base-radix integer literal optionally preceded by '+' or '-' (with no
space in between) and optionally surrounded by whitespace. A base-n
literal consists of the digits 0 to n-1, with 'a' to 'z' (or 'A' to 'Z')
having values 10 to 35. The default radix is 10. The allowed values are0
and 2-36, with 0 the same as 10.
>
If 0 is not the same as 10, the last would have to be changed, but I could
not detect any difference in a quick test.

One thing though, I think it should say "may be surrounded by
whitespace" as opposed to "optionally surrounded by whitespace".

On Apr 7, 1:55 am, Grant Edwards <gra...@visi.co mwrote:

On 2008-04-06, Lie <Lie.1...@gmail .comwrote:
>

I've noticed some oddly inconsistent behavior with int and float:

>

Python 2.5.1 (r251:54863, Mar 7 2008, 03:39:23)
[GCC 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)] on linux2

>>int('- 345')

-345

>

works,

>
IMO, it oughtn't.
>

>>float('- 345.083')

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for float(): - 345.083

>
That's the behavior I'd expect.

Sorry to confuse you, by works I mean that the interpreter doesn't
complain at all, I didn't mean that it works as it should be.

**Mark Dickinson** · Apr 8 '08, 01:25 AM

Re: A funnily inconsistent behavior of int and float

On Apr 7, 4:59 pm, "Terry Reedy" <tjre...@udel.e duwrote:

"Mark Dickinson" <dicki...@gmail .comwrote in message
>
news:1255ee3e-cc1e-4ae8-96f3-5f942c389c49@t5 4g2000hsg.googl egroups.com...
>
Thank you for the corrections. Here is my revised proposal:
>
int([number | string[, radix])
...

Excellent!

It looks to me as though this covers everything. I'm tempted to
quibble
about exact wordings, but probably the most productive thing to do
would
be just to submit this to bugs.python.org and then let Georg Brandl
work
his magic on it. :-)

Mark

**Terry Reedy** · Apr 8 '08, 02:35 AM

Re: A funnily inconsistent behavior of int and float

"Mark Dickinson" <dickinsm@gmail .comwrote in message
| Excellent!
| It looks to me as though this covers everything. I'm tempted to
| quibble about exact wordings, but probably the most productive thing to
do
| would be just to submit this to bugs.python.org and then let Georg Brandl
| work his magic on it. :-)

Issue 2580: Revise builtin class int library manual entry - Python tracker

http://bugs.python.org/issue2580

tjr

A funnily inconsistent behavior of int and float

A funnily inconsistent behavior of int and float

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