# 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
``````
1
59
7/2/2009 5:26:15 PM

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

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.

120
1/27/2014 8:40:35 PM

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.