randomly select 3 numbers whose sum is 356 and each of these 3 is more than 30
This question is rather subjective to the definition of random, and the distribution you wish to replicate.
The simplest solution:

Choose a one random number, rand1 : [30,296]
Choose a second random number, rand2 : [30, (326-Rand1)]
Then the third cannot be random due to the constraint so calc via 356-(rand1+rand2)
please how can I randomly select 3 numbers whose sum is 356 and each of these 3 is more than 30?
So output should be for example [100, 34, 222]
(but not [1,5,350])
I would like to use random module to do this. thank you!