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, Madam Noraslinda Asat, 34, screamed.
Her husband had seen the shadow of the snake through the foldable plastic door.
He said it was as thick as his forearm.
Mr Mohammad Fitri Kassim, also 34, who is self-employed, recounted the incident which happened last Thursday evening.
She was in the bathroom of the master bedroom of their first-storey Block 826 Eunosville home at Sims Avenue.
Madam Noraslinda said she had just sat down when she heard a soft bubbling noise, and felt a pain. The housewife said: "I looked down and it was 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 of 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 her shock, Madam Noraslinda felt weak and drowsy, so 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", said 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."