She had just sat down on the toilet bowl when she felt a sharp pain.
She looked down and saw a 1.8m-long python writhing in the toilet bowl, its jaws clamped on the back of her right thigh.
Petrified, Noraslinda Asat, 34, screamed.
Her husband, who had seen the shadow of the snake through the folding plastic door, said it was as thick as one of his forearms.
Mohammad Fitri Kassim, self-employed and also 34, recounted the incident, which happened on the evening of May 1.
His wife was in the bathroom of the master bedroom of their first-storey home at Block 826, Eunosville, in Sims Avenue.
Madam Noraslinda said she had just sat down when she heard a soft, bubbling noise and felt pain. The housewife said: "I looked down and I saw a snake."
She stood up and tried to grab the snake. But its body was so wide, it kept slipping out of her grip.
She said: "So I grabbed the head and pulled it off me. Then I backed out of the toilet and shut the door."
Their four-year-old daughter - Adriana, who had used the toilet five minutes earlier without incident - told Madam Noraslinda: "Mama, your tail was moving."
After the shock, Madam Noraslinda felt weak and drowsy. Mr Fitri called an ambulance, which took her to Changi General Hospital, where she was given an injection and discharged.
Doctors and nurses praised her bravery. They said "most girls would have fainted", according to Mr Fitri.
Describing the snake, Madam Noraslinda said: "It was brown, with patches of dark brown. I could tell it was a python. It was really long, I couldn't even see its tail in the toilet bowl."
Officers from the Animal Concerns Research and Education Society were called by police to capture the snake.