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Chris Withers

8 Feb 2013 8 Feb '13

3:39 p.m.

Hi All, Just had a bit of an embarrassing incident in some code where I did: sometotal =+ somevalue I'm curious why this syntax is allowed? I'm sure there are good reasons, but thought I'd ask... Chris -- Simplistix - Content Management, Batch Processing & Python Consulting - http://www.simplistix.co.uk

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Donald Stufft

8 Feb 8 Feb

3:41 p.m.

On Friday, February 8, 2013 at 10:39 AM, Chris Withers wrote:

Hi All,

Just had a bit of an embarrassing incident in some code where I did:

sometotal =+ somevalue I'm guessing this gets parsed as sometotal = +somevalue

I'm curious why this syntax is allowed? I'm sure there are good reasons, but thought I'd ask...

Chris

-- Simplistix - Content Management, Batch Processing & Python Consulting - http://www.simplistix.co.uk _______________________________________________ Python-Dev mailing list Python-Dev@python.org (mailto:Python-Dev@python.org) http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/donald.stufft%40gmail.com

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Benjamin Peterson

3:42 p.m.

2013/2/8 Chris Withers :

Hi All,

Just had a bit of an embarrassing incident in some code where I did:

sometotal =+ somevalue

That's just a strange way of expressing sometotal = +somevalue

I'm curious why this syntax is allowed? I'm sure there are good reasons, but thought I'd ask...

-- Regards, Benjamin

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Chris Angelico

3:42 p.m.

On Sat, Feb 9, 2013 at 2:39 AM, Chris Withers wrote:

Hi All,

Just had a bit of an embarrassing incident in some code where I did:

sometotal =+ somevalue

I'm curious why this syntax is allowed? I'm sure there are good reasons, but thought I'd ask...

For the same reason that you can negate a value with: sometotal = -somevalue The unary + and - operators are seldom problematic. ChrisA

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Xavier Morel

3:50 p.m.

On 2013-02-08, at 16:39 , Chris Withers wrote:

Hi All,

Just had a bit of an embarrassing incident in some code where I did:

sometotal =+ somevalue

I'm curious why this syntax is allowed? I'm sure there are good reasons, but thought I'd ask…

sometotal = (expression) is valid syntax, and +value is valid syntax. Thus what you wrote is perfectly normal syntax, it's the assignment of a pos'd value, badly formatted. pep8.py will warn against it (it'll complain that the whitespace around `+` is wonky). But I see no justification for disallowing this, anymore than for disallowing the rougly equivalent (and just as error-prone) `sometotal = -somevalue`.

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Oscar Benjamin

3:52 p.m.

On 8 February 2013 15:39, Chris Withers wrote:

Hi All,

Just had a bit of an embarrassing incident in some code where I did:

sometotal =+ somevalue

I'm curious why this syntax is allowed? I'm sure there are good reasons, but thought I'd ask...

Because '+' can represent an unary prefix operator just the same as '-':

...
...
+ + -- ++- +- -+ ++3 -3

Oscar

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Serhiy Storchaka

4:03 p.m.

On 08.02.13 17:39, Chris Withers wrote:

Just had a bit of an embarrassing incident in some code where I did:

sometotal =+ somevalue

I'm curious why this syntax is allowed? I'm sure there are good reasons, but thought I'd ask...

And why this syntax is allowed? pi = 3,14 And this: fruits = [ 'apple', 'pear', 'banana' 'ananas', 'mango' ]

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Chris Withers

4:05 p.m.

On 08/02/2013 15:42, Benjamin Peterson wrote:

2013/2/8 Chris Withers:

...
Hi All,

Just had a bit of an embarrassing incident in some code where I did:

sometotal =+ somevalue

That's just a strange way of expressing

sometotal = +somevalue

Indeed, but why should this be possible? When could it do something useful? :-) Chris -- Simplistix - Content Management, Batch Processing & Python Consulting - http://www.simplistix.co.uk

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Benjamin Peterson

4:10 p.m.

2013/2/8 Chris Withers :

On 08/02/2013 15:42, Benjamin Peterson wrote:

...
2013/2/8 Chris Withers:

...
Hi All,

Just had a bit of an embarrassing incident in some code where I did:

sometotal =+ somevalue

That's just a strange way of expressing

sometotal = +somevalue

Indeed, but why should this be possible? When could it do something useful? :-)

+ is a normal overridable operator. -- Regards, Benjamin

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Oscar Benjamin

4:17 p.m.

On 8 February 2013 16:10, Benjamin Peterson wrote:

2013/2/8 Chris Withers :

...
On 08/02/2013 15:42, Benjamin Peterson wrote:

...
2013/2/8 Chris Withers:

...
Hi All,

Just had a bit of an embarrassing incident in some code where I did:

sometotal =+ somevalue

That's just a strange way of expressing

sometotal = +somevalue

Indeed, but why should this be possible? When could it do something useful? :-)

+ is a normal overridable operator.

Decimal.__pos__ uses it to return a Decimal instance that has the default precision of the current Decimal context:

...
...
from decimal import Decimal d = Decimal('0.33333333333333333333333333333333333333') d Decimal('0.33333333333333333333333333333333333333') +d Decimal('0.3333333333333333333333333333')

Oscar

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Chris Withers

5:45 p.m.

On 08/02/2013 16:17, Oscar Benjamin wrote:

Decimal.__pos__ uses it to return a Decimal instance that has the default precision of the current Decimal context:

...
...
...
from decimal import Decimal d = Decimal('0.33333333333333333333333333333333333333') d Decimal('0.33333333333333333333333333333333333333') +d Decimal('0.3333333333333333333333333333')

That's the answer I was hoping wouldn't be coming... Oh well, guess I'll have to improve on my sloppy typing. Chris -- Simplistix - Content Management, Batch Processing & Python Consulting - http://www.simplistix.co.uk

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Xavier Morel

8:36 p.m.

On 2013-02-08, at 18:45 , Chris Withers wrote:

On 08/02/2013 16:17, Oscar Benjamin wrote:

...
Decimal.__pos__ uses it to return a Decimal instance that has the default precision of the current Decimal context:

...
...
...
from decimal import Decimal d = Decimal('0.33333333333333333333333333333333333333') d Decimal('0.33333333333333333333333333333333333333') +d Decimal('0.3333333333333333333333333333')

That's the answer I was hoping wouldn't be coming...

Oh well, guess I'll have to improve on my sloppy typing.

Or just run flake8 (with a bit of configuration to disable the annoying stuff).

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Ian Cordasco

9:35 p.m.

On Feb 8, 2013 3:37 PM, "Xavier Morel" wrote:

On 2013-02-08, at 18:45 , Chris Withers wrote:

...
On 08/02/2013 16:17, Oscar Benjamin wrote:

...
Decimal.__pos__ uses it to return a Decimal instance that has the default precision of the current Decimal context:

...
...
...
from decimal import Decimal d = Decimal('0.33333333333333333333333333333333333333') d Decimal('0.33333333333333333333333333333333333333') +d Decimal('0.3333333333333333333333333333')

That's the answer I was hoping wouldn't be coming...

Oh well, guess I'll have to improve on my sloppy typing.

Or just run flake8 (with a bit of configuration to disable the annoying

stuff). As flake8's maintainer, I second this.

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participants (8)

Benjamin Peterson
Chris Angelico
Chris Withers
Donald Stufft
Ian Cordasco
Oscar Benjamin
Serhiy Storchaka
Xavier Morel