CODEWITHSUNDEEP
pythonif-statementconditional-statementsbooleanalgebra
syllogismos
syllogismos

Reputation: 660

Instead of using several if statements I want to use a boolean algebra,

I want to use boolean algebra instead of several conditionals, for example

def boo(x,y):
    if x==3 and y==1: return 4
    if x==3 and y==4: return 1
    if x==4 and y==1: return 2
    if x==4 and y==2: return 1
    if x==5 and y==1: return 3

what I want to do is

def simple(x,y):
    return x#y

and there are total 12 equations, I just want to directly return (x#y) where # is a boolean operator. I did this to a smaller problem where I luckily found out a relation. I want to do the same in this case also, how do I proceed with it?

Does this have any performance gains, because its not going through several if conditionals? Is this normal practice?

sample:

 x    y   output
 1    2     3
 1    3     2
 1    4     5
 1    5     4

here a simple bitwise xor gate will do

def(x,y): return x^y

Upvotes: 0

Views: 574

Answers (3)

zallarak
zallarak

Reputation: 5515

You could consider using dictionaries. You could perhaps make a dictionary of dictionaries, and have your function retrieve values through the dictionary.

def boo(x,y):
    if x==3 and y==1: return 4
    if x==3 and y==4: return 1
    if x==4 and y==1: return 2
    if x==4 and y==2: return 1
    if x==5 and y==1: return 3

def boodict(x,y):
    d1 = {3: {1:4, 4:1} ,4: {1:2, 2:1},5: {1:3}}
    try:
        value = d1[x][y]
    except KeyError:
        value = None
    return value

Upvotes: 0

Marcelo Cantos
Marcelo Cantos

Reputation: 185852

I don't know whether trying to find a terser expression of the above logic would lead to more readable code; probably not. But you can rework the logic as-is to a more mathematical formulation:

def boo(x, y):
    p = (x, y)
    return (1 if p in ((3, 4), (4, 2)) else
            2 if p == (4, 1) else
            3 if p == (5, 1) else
            4 if p == (3, 1) else
            None)

Another option is to use a dictionary:

def boo(x, y):
    return {(3,4):1, (4,2):1, (4,1):2, (5,1):3, (3,1):4}.get((x, y), None)

If you know that all values will match the specified cases, you can write [(x, y)] instead of .get((x, y), None).

Upvotes: 1

Adam Zalcman
Adam Zalcman

Reputation: 27233

You can find the right expression that yields the same values as your conditionals, but such code becomes harder to read and maintain.

A better solution is to use a nested list or dictionary which you can index with input values. This way you turn code into data which is a clear and fast representation of your mapping and which can be readily understood and easily modified in the future.

Upvotes: 2

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