python not operator with parenthesis

Question

I have a simple logic if statement returning an invalid syntax error. The statement is:

if (a[1] != None and a[2] != None and !(a[3] == None and a[4] == None)):

The invalid syntax is the third ! operator. Any reason why this would not work? Is there another operator I am supposed to use in this situation?

So the logic is essentially: a[1] ^ a[2] ^ (a[3] v a[4]) (where these denote having values). Hence the reverse logic for getting no None values is:

!a[1] ^ !a[2] ^ !(a[3] ^ a[4])

I'm pretty sure my logic maths is right, so how do I get the result I require?

*Background info: Python 2.7.10, overall code is pulling data out of an SQL Server 2008 table, manipulating it and then inserting it into a different table that doesn't allow NULL values, and the original table is littered with NULLs

Thanks for your help!

score 6 · Accepted Answer · answered Oct 19 '15 at 02:34

6

The logical not operator in python is not ! but rather is not.

You want:

if (a[1] != None and a[2] != None and not (a[3] == None and a[4] == None)):

answered Oct 19 '15 at 02:34

Gort the Robot

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Yep that did the trick. Thank you for the quick response. Have to wait 10 mins to accept the value.... – Aaron Troeger Oct 19 '15 at 02:36
@shawn-mehan is right, by the way. My suggestion was just the minimal change to make it run. – Gort the Robot Oct 19 '15 at 02:39

score 2 · Answer 2 · answered Oct 19 '15 at 02:37

2

Well, stylistically, when using None it is preferred to use is and is not rather than == and !=, so

if (a[1] is not None and a[2] is not None) and not (a[3] is None and a[4] is None):

answered Oct 19 '15 at 02:37

Shawn Mehan

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python not operator with parenthesis

2 Answers2