How do you divide a list (indefinite length) randomly into 3 subgroups?

Lets say that my program asks a user to input a number indefinitely and I appended it in a list.

#Given Example:
List = [105, 167, 262, 173, 123, 718, 219, 272, 132]

what I wanted to do is to randomly pick any of the numbers so my sample output would be:

first = [105, 262, 173]
second = [167, 123, 132]
third = [718, 219,272]

Having said, since the user input would be indefinite there will be chances that it would be an odd number.

I am currently using random.sample to choose a number from that list and append it in a list, after that I'll append the sub-groups of list to create a list within a list.

Would be a great help if anyone answers, thanks!