Using the AND and NOT Operator in Python [duplicate]

Question

Here is my custom class that I have that represents a triangle. I'm trying to write code that checks to see if self.a, self.b, and self.c are greater than 0, which would mean that I have Angle, Angle, Angle.

Below you will see the code that checks for A and B, however when I use just self.a != 0 then it works fine. I believe I'm not using & correctly. Any ideas? Here is how I am calling it: print myTri.detType()

class Triangle:      # Angle A To Angle C Connects Side F     # Angle C to Angle B Connects Side D     # Angle B to Angle A Connects Side E      def __init__(self, a, b, c, d, e, f):         self.a = a         self.b = b         self.c = c         self.d = d         self.e = e         self.f = f      def detType(self):         #Triangle Type AAA         if self.a != 0 & self.b != 0:             return self.a          #If self.a > 10:             #return AAA          #Triangle Type AAS          #elif self.a = 0:             #return AAS          #Triangle Type ASA          #Triangle Type SAS          #Triangle Type SSS            #else:             #return unknown 

Answer 1

You should write :

if (self.a != 0) and (self.b != 0) : 

"&" is the bit wise operator and does not suit for boolean operations. The equivalent of "&&" is "and" in Python.

A shorter way to check what you want is to use the "in" operator :

if 0 not in (self.a, self.b) : 

You can check if anything is part of a an iterable with "in", it works for :

• Tuples. I.E : "foo" in ("foo", 1, c, etc) will return true
• Lists. I.E : "foo" in ["foo", 1, c, etc] will return true
• Strings. I.E : "a" in "ago" will return true
• Dict. I.E : "foo" in {"foo" : "bar"} will return true

As an answer to the comments :

Yes, using "in" is slower since you are creating an Tuple object, but really performances are not an issue here, plus readability matters a lot in Python.

For the triangle check, it's easier to read :

0 not in (self.a, self.b, self.c) 

Than

(self.a != 0) and (self.b != 0) and (self.c != 0)  

It's easier to refactor too.

Of course, in this example, it really is not that important, it's very simple snippet. But this style leads to a Pythonic code, which leads to a happier programmer (and losing weight, improving sex life, etc.) on big programs.

Answer 2

Use the keyword and, not & because & is a bit operator.

Be careful with this... just so you know, in Java and C++, the & operator is ALSO a bit operator. The correct way to do a boolean comparison in those languages is &&. Similarly | is a bit operator, and || is a boolean operator. In Python and and or are used for boolean comparisons.