Create Dynamic For Loop

[quest]

Hello
My number of sublists is in this line:

        number_of_sublist=sum(len(x) for x in incoming)
      

And I want to create a for loop till the this number. For instance if number_of_sublist=2, then I need to create 2 forloop:

for x in incoming:
         for y in x:

If number_of_sublist=4, then I need to create 4 for loop like that:

for x in incoming:
    for y in x:
       for z in y:
        for t in z:
...    

How can I do that in an efficient way?