Randomizing Load Condition w/ OSPAN

I am looking to randomize load condition during an OSPAN task such that each load condition (2, 3, 4, 5 problems) appears 3 times each throughout the experiment. Each load condition will be its own block, therefore I need to randomize block length and ensure that each block length appears 3 times. I am extremely new to PsychoPy and would appreciate any guidance! Thank you!

Sarah