Venins (1991)

Marc, a young snake expert, works at a museum in Geneva. He loves snakes, to the point that he owns many and even takes a bath with his huge pet python. He meets and falls in love with a beautiful young woman named Malenka, who is the assistant--and mistress--of an older herpetologist professor. Marc discovers that not only is the "professor" a fraud but also a dangerous psychotic who had at one time seduced Marc's mother, and Marc believes that the longer Malenka stays with him, the greater danger she's in.

Unfortunately the movie Venins is not yet available on HBO Max.