Python's Equivalent of && (Logical-And) in an If-Statement

Python's equivalent of && (logical-and) in an if-statement

Use and instead of &&.

Using IF, AND, OR together with EQUAL operand together in Python

It helps to examine the logic of this line:

if (len(x) == (4 or 6)):

The (4 or 6) clause contains a logical or short circuit. The value 4 is true, so it is evaluated and returned to the == relational comparison.

The way that or works is that its lefthand side is evaluated for Boolean truth, and its value is returned if true. If the lefthand side is not Boolean true, then the righthand side is evaluated and its value is returned.

Because the lefthand side of the 4 or ... is true in a Boolean sense, the righthand side is never evaluated. Python doesn't even look past 4 or. If the left-hand value were a false value (such as 0), then the right hand side of the or would be evaluated.

To see this in action, try print 4 or 6. The output will be 4.

So since the 4 is a hard-coded true value, your comparison is semantically the same as if (len(x) == 4) -- that is, since 4 is true, 6 is never evaluated.

What I suppose you really want to know is if len(x) is either 4 or 6. You could put that to code in a couple of ways:

if(len(x) == 4 or len(x) == 6 ...

if(len(x) in (4,6) ...

How to have multiple conditions for one if statement in python

I would use

def example(arg1, arg2, arg3):
     if arg1 == 1 and arg2 == 2 and arg3 == 3:
          print("Example Text")

The and operator is identical to the logic gate with the same name; it will return 1 if and only if all of the inputs are 1. You can also use or operator if you want that logic gate.

EDIT: Actually, the code provided in your post works fine with me. I don't see any problems with that. I think that this might be a problem with your Python, not the actual language.

Python's Logical Operator AND

Python Boolean operators return the last value evaluated, not True/False. The docs have a good explanation of this:

The expression x and y first evaluates x; if x is false, its value is returned; otherwise, y is evaluated and the resulting value is returned.

Behaviour of bitwise AND and logical AND along with equality operator in Python 3

& has higher precedence than ==.

So this:

1110010110001000 == 1110010110001000 & 1 == 1 & 1000001000001101 == 1000001000001101 & 1 == 1

means

1110010110001000 == (1110010110001000 & 1) == (1 & 1000001000001101) == (1000001000001101 & 1) == 1

which means

1110010110001000 == 0 == 1 == 1 == 1

which means (due to operator chaining)

(1110010110001000 == 0) and (0 == 1) and (1 == 1) and (1 == 1)

which is false.

In summary, don't use & to mean logical and.

Python if statement not working correctly and no idea why

I believe you should be using "and" instead of "&" in the if statements. You can read up on the differences here:

https://www.geeksforgeeks.org/difference-between-and-and-in-python/

Using the AND and NOT Operator in Python

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.

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