Randomnly select numbers from a list with a condition

I have a list(range(30000)). I need to randomnly select numbers inside it such that, it takes a certain count of numbers say 'n' in total at the same time it should take 'k' number of values between two index positions.

For example:

a = [1,2,3,4,5,,6,7,8......20,21,22......88,89.....30k]

I need to select 5000 numbers in total. 'x' numbers between 0th index to 100th index, 'y' numbers between 100 to 200 etc.

There is no hard rule that it should select 5000 numbers itself. But it should sure lie between 0-100, 100-200 etc.

I saw random.choice but how to give it a condition

To put the question accurately: I need 50 numbers from 0-100,200-300 etc.