Creating a Python list or dictionary with a set number of rows, but variable number of columns per row

Question

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.

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.

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?

If you create a list where each element is a list, you get a list of lists, and each sublist can have its own size. — Haroldo_OK
– Haroldo_OK, Commented Aug 1, 2016 at 18:57

Scimonster · Accepted Answer · 2016-08-01 18:57:01Z

1

How about something like this?

row1 = [1,2,3,4,5,6]
row2 = [1,2,3]

matrix = [row1, row2]

row3 = [1,2,4,5,6,7,8,9]
matrix.append(row3)

answered Aug 1, 2016 at 18:57

Scimonster

33.4k10 gold badges79 silver badges92 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

user6664585 Over a year ago

Since it isn't possible to append to a list that hasn't been initialized, is there any way of not specifying what goes in "matrix"?

Scimonster Over a year ago

@user6664585 Just initialize it to an empty list. matrix = []

Collectives™ on Stack Overflow

Creating a Python list or dictionary with a set number of rows, but variable number of columns per row

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related