Creating a Python list or dictionary with a set number of rows, but variable number of columns per row
<p>I'm working with images and want to create a list of lists of arrays. For example, a list with 5 rows, where each row has a variable number of images (3x200x100) stored in them ranging from 2 images to 10 images.</p>

<p>I've ruled out numpy and concatenation since they need the matrix to be uniform. I've tried appending one list to another, but that just gives me a long row of them when what I want is another row to be added after the prior row.</p>

<p>I was thinking that either a list or a dictionary would be the way to go since what I'm using to populate my list of lists is a dictionary, but I'm unable to figure out how to structure the lists so that it's correct to my above specifications instead of just a super long list. Is there any way for me to initialize a list so that only the row number gets specified and I can dynamically change the column number per row? If not, is there a different data structure I should be looking at?</p>