Using the AND and NOT Operator in Python

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

Use the keyword "and", not &. & 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.

Answer 2

It's called "and" and "or" in Python.

Answer 3

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 O 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 :

O not in (self.a, self.b, self.b)

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 loosing weight, improving sex life, etc) on big programs.