What is the difference between logical operators and their corresponding chained if-conditionals?

Question

I'm a beginner in python and I was studying logical operators.

Say, we have two boolean expressions, c1 and c2. We can define a function

def and_operator(c1,c2):
    if (c1 == False):
        return False
    elif (c2 == False):
        return False
    else:
        return True

This function gives the same output that the and operator applied on c1 and c2 would give.

So, at the fundamental level, is there any difference between how these two approaches work? Is there any difference between the two methods other than the latter making the code significantly easier to write and read?

Answer 1

The and operator does not evaluate the second expression if the first one is False, because it already knows the final result will be False no matter what. Your function, however, evaluates both conditions upfront, which can lead to unnecessary computation, especially if c2 value comes from heavy calculations, complex or resource-intensive operation.

Answer 2

In my opinion,using the AND operator has its benefits: 1)widely known and easy to understand by "newer" coders. 2)will work better for different types of variables,your code only applied for booleans. 3)short circle evaluation

Answer 3

The difference is at the cpu level. CPUs nowdays come with dedicated logical operation instructions. If you use them, you can significantly speed up your code. that's how the and operator in python and most other languages is implemented. Whereas your approach is also logically correct but it has performance drawbacks. Firstly, the code will have multiple jmp (jump) statements at the CPU level because you are using conditions such as if-else. The second problem is, Python is slow, it really is. so writing it in your way will also cause more performance drawbacks. Now think of it, what would be more beneficial

1. having a single instruction that completes execution within a single cpu cycle
2. having a big atleast a few hundred set of instructions that complete after multiple cpu cycles

ofcourse, everyone would go for option 1, hence the reason why we use the and operator. even the python interpreter itself uses and operator defined by its parent language C. C internally uses the and operator defined by the assembler. and well, assembler uses the "and" instruction defined by the CPU.

There is no such thing as defining "and". it is defined at the hardware level.

As for performance, lets have a look:

import timeit

def and_operator(c1,c2):
    if (c1 == False):
        return False
    elif (c2 == False):
        return False
    else:
        return True

def f1():
    a = True
    b = True
    this = a and b
    return this

def f2():
    a = True
    b = True
    this = and_operator(a, b)
    return this


t1 = timeit.timeit(f1)
t2 = timeit.timeit(f2)

print("Time 1: ", t1)
print("Time 2: ", t2)

print("Time 1 is", t2/t1, "times faster than Time 2")

this outputs:

Time 1:  0.05105140000523534
Time 2:  0.1449641000072006
Time 1 is 2.8395714905435403 times faster than Time 2

weirdly enough, python optimized my test code and hence the factor is only 2.8, in reality if python hadn't optimized my test code, this could have been well around 100.

Answer 4

Both logical operators and chained if-conditionals can achieve similar results, but there are some differences between them:

Logical operators are built-in symbols like and, or, and not that operate directly on boolean values (True or False). They evaluate both operands and return a single boolean result based on the specific operator's logic (e.g., and returns True only if both operands are True). They typically perform short-circuit evaluation, meaning they stop evaluating operands as soon as they can determine the final result. For example, and stops evaluating the second operand if the first is False. This can improve efficiency if one operand is expensive to compute. Chained if-conditionals: They evaluate each condition in sequence, regardless of whether the result is already determined. This can be less efficient if some conditions are expensive to compute Chained if-conditionals involve using multiple if statements one after another, checking each condition in sequence. Each if statement's block of code only executes if its condition is True. If any condition is False, the remaining if statements are skipped.they are often preferred for simple expressions due to their conciseness, readability, and potential efficiency gains from short-circuit evaluation. Chained if-conditionals are more suitable for complex logic or when you need more control over the evaluation flow.