They say the incident happened just before 10 pm last night outside Cost Cutter in Colomberie at the top of town.
Police say the woman and her attacker were known to each other, and he is described as having dark hair, and dressed at the time in blue jeans and a grey and blue V-neck top.
The lady was sat with her toddler in a black VW Golf.
Another man tried to step in and help them, but the police believe he was also assaulted by the man.
Police say the incident attracted a crowd and anyone with any information about the assault is asked to contact them on 612612 or Crimestoppers anonymously on 0800 555111.
