All right, I’ll admit it. I’m attracted to Diane Keaton in “Something’s Gotta Give.”

There’s something very infectious about the way she characterizes her role: She hits every line with just the right amount of comic energy, she carries herself well — and physically speaking, let’s admit it, Keaton’s looking pretty good.

These are all reasons why Jack Nicholson’s character falls for her in only days — a convention in movies that rarely works yet waives the disbelief in this film.

Nicholson plays Harry, a 63-year-old womanizing recording industry mogul who lives by the credo of never dating anyone past the age of 30. He thinks he’s off for an affair in the Hamptons with his new girlfriend, played by Amanda Peet, but he’s caught unzipped by her bitchy playwright mother, Erica, played by Keaton.

Aside from a huge laugh supply, “Something’s Gotta Give” coasts along due to the chemistry of its stars. Keaton and Nicholson work so well onscreen together it’s enjoyable to see them in the same frame.

Despite some rather gaping flaws, the film was carrying on as an easily recommendable romantic comedy. Laughs were sometimes juvenile, but nevertheless extremely funny.

But it was all an awkward success. A charade of a success, but damn it if it didn’t work until the film’s conventions eventually caved in.

My annoyance with the film stems from writer-director Nancy Meyers’s thinly veiled love for her own idea. Erica, eventually driven to heartache, writes her newest hit based upon her experiences with Harry.

Logic flies out the window for two reasons: Meyers’ idea, which is the screenplay to the movie, is supposedly the best work of a highly respected playwright. Secondly, a romantic comedy asks its audience to suddenly buy into the conventions of an art-imitating-life scenario. The film changes its narrative from weightless fluff to heavy-handed cautionary tale of love — and this is supposed to be a comedy about maturity and romance after 50.

Thankfully, there’s still Keaton: She saves the film. Everyone else is either given too little screen time to develop or just snoozing. Nicholson never oversteps playing, yet again, a slight alteration of himself in real life.

Keaton, however, provides her best performance in years — and maybe decades. When Nicholson and Reeves are too busy looking embarrassed to be there, she’s creating a strong female presence.

By physically reserving herself from the absurdities of Meyers’ script, she sets herself apart from it. That’s great acting, and reason enough to see the film.