Specific randomization, help :C

OS: windows 10
PsychoPy version: v2022.1.3

What are you trying to achieve?:
mrt_training_1.psyexp (778.1 KB)

I apologize for my English. but i’m not a native speaker.
I am designing a study that presents images (337 for easy, 2177 for hard, 1058 for medium) divided into 3 difficulties.
I divided each difficulty into a separate routine. The stimuli are loaded through an .xlsx file (one for each difficulty).
I know how to randomize a block of routines. and forms of randomization of different levels.
what I need to do is: present the stimuli using the following sequence: 7 “easy stimuli”, 2 “medium stimuli” and 1 "hard stiumuli) in a loop for 30 minutes. The stimuli must be randomly selected from the library of stimuli that I made depending on their difficulty.

I have been looking for solutions for many days but it escapes my current knowledge.

AID!!

mrt_training_1.psyexp (778.1 KB)

Hello,
I had a similar problem and I solved it with these two answers:

I hope it works for you