To GUEST-woman walking dark alley, firstly try not to be there, ie=
get a taxi, or a lift home if possible, if not possible then carry a Maglite Torch [the sort the police use], if anyone hassles you, smack them across the head with it, be sure you have good reason to though, as they can cause serious damage!
if he is no immediate threat, ie he just looks at you in a bad way, then jab him in the guts with it as hard as possible, also useful for repelling dangerous dogs [smack downwards onto their skull].