Python 3 conditional variable selection increment

Question

I'm currently working on a project where a lot of different accounting is done and I came to see this pattern very often:

if A > X:
    B += 1
else:
    C += 1

I know ternary operator but if I understand it correctly the shortest way how to utilize it would be:

B += 1 if A > X else False
C += 1 if A <= X else False

since ternary operator is connected to the variable used in its head. So using ternary operator is obviously worse than the previous if/else both from computational and readability standpoint.

The other idea was to create a simple function like this:

conditional_bumper(positive_case_var, negative_case_var, condition_var, compare_to=0)

then the usage looks like:

conditional_bumper(B, C, A, X)  # X being optional

so I can one line it every time I see it but at the same time this seems to me like a very 'hacky' solution. Is there a better way I don't see?

Seems like you are counting the number of times that A > X. If this is a case, there is probably a way you can utilize collections.Counter — DeepSpace
– DeepSpace, Commented Oct 8, 2020 at 12:59
If you don't care about readability at all, you could write this even shorter as B += A > X; C += A <= X - your second code block is relying on the fact that False has a numeric value of 0, might as well rely on True having a value of 1 as well. — jasonharper
– jasonharper, Commented Oct 8, 2020 at 13:00
@VPfB Using 0 if A>X else 1 is a bit counter-intuitive (especially if treating 0 as the "truthy" case) since booleans can be used as keys directly. See my answer — DeepSpace
– DeepSpace, Commented Oct 8, 2020 at 13:29

Alvison Hunter · Accepted Answer · 2022-01-29 05:08:15Z

3

Try this Pal! Hope this gives you a north of this matter. Cheers!

    # declare and initialize variables
    B, C = 0, 0
    A, X = 1, 2
    
    # ternary operator to work with this conditional
    B,C = (B + 1, C) if A > X else(B,C + 1)
    
    #display results
    print(B,C)

answered Jan 29, 2022 at 5:08

Alvison Hunter

6835 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

eXPRESS Over a year ago

Thanks, this seems as the best option so far. :)

Alvison Hunter Over a year ago

Glad to be of help, pal!

marcoAndrew · Accepted Answer · 2020-10-08 13:04:58Z

1

I think that the more readable you'r code is, the better is. " One line " code works but it's not viable

answered Oct 8, 2020 at 13:04

marcoAndrew

516 bronze badges

1 Comment

eXPRESS Over a year ago

I agree with you, I don't want to sacrifice readability I simply wonder if I can get better solution overall because in a way having that original pattern in the code makes it long and less readable.

DeepSpace · Accepted Answer · 2020-10-08 13:25:51Z

1

If you are really after a one-liner and don't care about readability (which you shouldn't), you can use this old trick (at the cost of building a list and having a somewhat cryptic code)

A = 2
B = 0
C = 0
X = 3

CB = [C, B]
print(CB)
CB[A > X] += 1
print(CB)

# [0, 0]
# [1, 0]

Note that C and B themselves are not modified, the change is only visible through the CB list.

This works because A > X evaluates to True or False, which can be used for indexing since bool subclasses int.

A better approach using a dict

Another less cryptic option is to use a dict instead. I think this is actually a better option. You can even use meaning full names :)

A = 2
X = 3

times_a_greater_than_x = {True: 0, False: 0}
times_a_greater_than_x [A > X] += 1
print(times_a_greater_than_x )
# {True: 0, False: 1}

edited Oct 8, 2020 at 13:25

answered Oct 8, 2020 at 13:20

DeepSpace

82.1k12 gold badges119 silver badges166 bronze badges

1 Comment

eXPRESS Over a year ago

I appreciate the creativity of these! :) It could even scale up for more conditions and vars if certain ordering was followed but in that case I would have to accept that someone would kill me eventually (and rightly so).

Wups · Accepted Answer · 2020-10-08 13:59:31Z

1

Enhancing the idea of using a function:

def inc_if(condition, true_var, false_var):
    if condition:
        true_var += 1
    else:
        false_var += 1

    return (true_var, false_var)


B, C = inc_if(A > X, B, C)

This is quite readable because it can be read from left to right as "increment if A > X" followed by the variable that would be in the if clause and at last the variable from the else clause.

The variables need to be returned by the function and reassigned, unless global variables are used.

answered Oct 8, 2020 at 13:59

Wups

2,5691 gold badge8 silver badges17 bronze badges

1 Comment

eXPRESS Over a year ago

Good improvement, the reassignment is necessary as you point out. Sadly it also makes it computationally more expensive hence it seems that staying with the original is the only reasonable course of action.

tripleee · Accepted Answer · 2021-02-08 12:44:40Z

1

If X varies across the conditionals but A, B, and C remain the same, you can refactor to a simple loop.

for X in (1, 2, 3, 5, 7, 13, 17, 23):
    if A > X:
        B += 1
    else:
        C += 1

answered Feb 8, 2021 at 12:44

tripleee

192k37 gold badges318 silver badges367 bronze badges

Comments

Hadrian · Accepted Answer · 2020-10-08 13:05:34Z

0

this isn't one line, but you can increment each variable by the increment times the boolean expression

inc = 1
B += inc * (A > X)
C += inc * (A < X)

or you can use this

inc = 1
B += inc * (A > X); C += inc * (A < X)

answered Oct 8, 2020 at 13:05

Hadrian

9477 silver badges11 bronze badges

1 Comment

VPfB Over a year ago

Two tests instead of one, two assignment instead of one, two multiplications instead of none .... not an improvement IMO

Collectives™ on Stack Overflow

Python 3 conditional variable selection increment

6 Answers 6

2 Comments

1 Comment

A better approach using a dict

1 Comment

1 Comment

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

2 Comments

1 Comment

A better approach using a dict

1 Comment

1 Comment

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related