Open Stack

Even better - it's actually special-cased and "x not in y" is exactly
equivalent to "not x in y".
Check out dis module:

In [13]: dis.disassemble((lambda a, b: a not in b).func_code)
  1           0 LOAD_FAST                0 (a)
              3 LOAD_FAST                1 (b)
              6 COMPARE_OP               7 (not in)
              9 RETURN_VALUE        

In [14]: dis.disassemble((lambda a, b: not a in b).func_code)
  1           0 LOAD_FAST                0 (a)
              3 LOAD_FAST                1 (b)
              6 COMPARE_OP               7 (not in)
              9 RETURN_VALUE        

(useful if your "not in" is faster or means something different than negated
"in" - for example bloom filters, etc.)

#things_you_never_expected_to_need

Regards,
Stanisław Pitucha
Cloud Services 
Hewlett Packard


-----Original Message-----
From: Dean Troyer [mailto:dtroyer at gmail.com] 
Sent: Thursday, January 31, 2013 4:20 PM
To: OpenStack Development Mailing List
Subject: Re: [openstack-dev] "if X not in Y" vs. "if not X in Y" consensus?

On Thu, Jan 31, 2013 at 9:57 AM, Vishvananda Ishaya <vishvananda at gmail.com>
wrote:

> The in operator has precedence over not so to have not be an operator 
> on X you would need:
>
> (not X) in Y

Ugh.

"It's morning" I thought
"I'll just look this up" I thought
"Yup, 'boolean not' is above 'in' (and the other operators) in the table" I
thought, without actually looking at the table and noticing that it's
backwards from every other operator precedence table I've looked at and
written "Python can't have more than one way to do this" I thought

Wrong.

/me going back to get more caffeine...

dt

-- 

Dean Troyer
dtroyer at gmail.com

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