# Errors. if 1 in (1,): print("Single-element tuple") if 1 in [1]: print("Single-element list") if 1 in {1}: print("Single-element set") if "a" in "a": print("Single-element string") if 1 not in (1,): print("Check `not in` membership test") if not 1 in (1,): print("Check the negated membership test") # Non-errors. if 1 in (1, 2): pass if 1 in [1, 2]: pass if 1 in {1, 2}: pass if "a" in "ab": pass if 1 == (1,): pass if 1 > [1]: pass if 1 is {1}: pass if "a" == "a": pass if 1 in {*[1]}: pass # https://github.com/astral-sh/ruff/issues/10063 _ = a in ( # Foo b, ) _ = a in ( # Foo1 ( # Foo2 # Foo3 ( # Tuple ( # Bar (b # Bar ) ) # Foo4 # Foo5 , ) # Foo6 ) ) foo = ( lorem() .ipsum() .dolor(lambda sit: sit in ( # Foo1 # Foo2 amet, )) ) foo = ( lorem() .ipsum() .dolor(lambda sit: sit in ( ( # Foo1 # Foo2 amet ), )) ) foo = lorem() \ .ipsum() \ .dolor(lambda sit: sit in ( # Foo1 # Foo2 amet, )) def _(): if foo not \ in [ # Before bar # After ]: ... def _(): if foo not \ in [ # Before bar # After ] and \ 0 < 1: ...