STEVE MARTIN'S ''L.A. Story'' is so perky, stylish and light it is over before you realize that there is very little substance to it.
That's all right. Who needs substance when the photography, the performers and the locale are as attractive as this?
Not that the film wants Los Angeles to look attractive. It means to put the city down and does. The humor, however, is gentle. The aim, at the same time, is true. ''We'll take a cultural tour of the city,'' says Martin, as TV weatherman Harris Telemacher. ''That should take 15 minutes,'' says Victoria Tennant, as the English journalist he is pursuing.
Martin did the script, and it has a number of workable gags. Some of the visual business is downright silly, undeserving of inclusion in this film, but most of the material plays well enough to encourage us to overlook the situations that do not.
Martin, as a writer, is not afraid to borrow. Part of his plot goes back to Noel Coward's ''Private Lives,'' and some of the other gags he uses have been around for several years.
Martin's gift, however, is that he is able to make us all laugh at this, new or old, even when he uses the joke about Mother Theresa, the one about the Pope asking her if he can do anything for her. Mother Theresa declines. The Pope persists. ''Well,'' says Mother Theresa, ''I would like to direct.''
Martin's weatherman is not all that accurate. He pre-tapes the forecast for the weekend, and when it rains, he is in trouble. He doesn't, however, care that much. He is too much smitten with Sara (Tennant), who has already been married and wants no more entanglement.
Telemacher, however, persists, with the aid of a highway sign that encourages him to live and enjoy his life. Whenever Telemacher is troubled, he goes back and talks to the sign.
Well, this is Los Angeles, and if it can happen anywhere, it can happen here.
Marilu Henner is the weatherman's girlfriend. He drops her, but don't worry about her. She's not the most faithful companion a man can have. Nor is Sandy, a 23-year-old woman who is never still. She is a one-woman aerobics class, always moving. She has a boyfriend, but he has encouraged her to date others, which she does.
The new film occasionally borders on brilliant. There is, for instance, the sequence in which Telemacher wants to make reservations at a popular restaurant and endures a rigorous credit check in the process. In another, all the diners at a posh restaurant order different kinds of coffee.
These are two of the better sequences that make the film worthwhile, and when the material isn't that lively, the direction is. It was done by Mick Jackson, who wants to convey the impression that this is a ditsy town and does so by keeping his cameras in flow, around, among and beyond his players.
''L. A. Story'' opens here today. At times, it plays a little like early Woody Allen, and that may be compliment enough.
*** A Los Angeles TV weatherman pursues a reporter for the London Times.
CAST: Steve Martin, Victoria Tennant, Marilu Henner, Richard E. Grant, Sarah Jessica Parker, Kevin Pollack
DIRECTOR: Mick Jackson
RATING: PG-13 (sex)
RUNNING TIME: 95 minutes