operators - Python: Concise way to toggle boolean "once" (i.e., in one direction) -

i find myself needing update boolean variable when happens first time (and then). using var = not var out of question since continue flip-flopping every time.

(sorry silly example; i'm struggling find more sensible one…)

inner_has_been_two = false outer in range(5):     inner in range(3):         if inner == 2:              if not inner_has_been_two:                 inner_has_been_two = true          print(inner_has_been_two) 

let's assume want "touch" variable little possible—otherwise overwrite again , again omitting innermost if-statement.

basically i'm looking more terse, pythonic way emulate (the binary versions of ternary conditional operator, like) elvis operator (?:) or null coalescing operator (e.g. ??; varies upon language).

any ideas on how keep short(er) , clear?

setting true each time fast: single machine cycle, easy parallel process. if want logically trying do:

inner_has_been_true |= true 

this single-cycle instruction, "bit set" operation. it's shorthand for

inner_has_been_true = inner_has_been_true | true