Invert boolean assignment in one line

Question

Is there a short way to do this:

if flag == False: flag = True

I feel like it should be only a few letters.
I'm also curious about how other languages tackle this condition-assignment. Thank you.

Edit

If flag is True it needs to stay True therefore I can't use flag = not flag.
flat = True is indeed a one-line solution but since the statement is inside a loop I'm not sure if reassigning flat = True every time is good practice.

(Assuming, of course, that flag was previously either False or True. Also, comparing to False with == is pretty much always either unnecessary or wrong.) — user2357112
– user2357112, Commented Nov 20, 2018 at 18:53
flag = not flag...at least I think that's what your asking for — Joran Beasley
– Joran Beasley, Commented Nov 20, 2018 at 18:53
You're making the classic newbie mistake of putting in more work to avoid an assignment than you actually save. Assignment is cheap. Heck, you're still performing the assignment in the answer you accepted; the accepted answer is strictly more expensive than flag = True. — user2357112
– user2357112, Commented Nov 20, 2018 at 21:42

Ryuzaki L · Accepted Answer · 2018-11-20 19:17:55Z

1

By using if-else do it in one line either True or `False

flag = True if 10<5 else False #(True if condition is True else False)

answered Nov 20, 2018 at 19:17

Ryuzaki L

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1 Comment

Ryuzaki L Over a year ago

Ya but in the above code there in no loop, and it completely depends on your requirement, everytime if you need to check condition then it is necessary, or if the requirement is just to assign flag once based on condition, then place it outside of loop

ritlew · Accepted Answer · 2018-11-20 18:54:26Z

0

Yes! You can simply invert it with a short expression:

flag = not flag

edited Nov 20, 2018 at 18:54

answered Nov 20, 2018 at 18:53

ritlew

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3 Comments

user2357112 Over a year ago

Python doesn't use !.

timgeb Over a year ago

but if flag is True this code will set it to False.

ritlew Over a year ago

According to the title I thought they were looking for a way to invert a boolean with one line

Bigbob556677 · Accepted Answer · 2018-11-20 18:56:34Z

For inline conditionals in general you could use

if flag == False: flag = True

or for just toggling a boolean you could use

flag = not flag

you could also use the ternary operator which is something like

flag = condition_if_true if condition else condition_if_false

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