Noah Clark Noah Clark - 27 days ago 11
Python Question

Using the AND and NOT Operator in Python

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 Source

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.