2D Lists - Lakelands Computing

2D Lists

A 2D, or 2 dimensional list, is effectively a list of lists. Take a look at the tables below and this will make more sense

index	0						1			2			3
value	cat, dog, pig						mice, bird, snake			fish, ant ,bear			mole, moose, horse

As you can see there is a list of three things in each index place in the list. If we ran this in Python:

print (animals[0])

It would print ["cat","dog","pig"]

As it is a list, we can split it down into its indexes too:

index	0			1			2			3
index	0	1	2	0	1	2	0	1	2	0	1	2
value	cat	dog	pig	mice	bird	snake	fish	ant	bear	mole	moose	horse

As you can see now there are two index numbers. This allows us to refer to a particular value:

print (animals[0][0])

It would print "cat"

print (animals[0][1])

would print "dog"

print (animals[1][0])

would print "mice"

You might be thinking what's the point of a 2D list, but think of it as maybe a list of contacts the index could be their reference number, and for each customer you could have name, phone, email. Use the trinket below to see how it actually runs. Maybe try and build and use a 2D list for the customer example..

Pay special attention to the way the 2D list is written:

There are the [ ] for the main list,
Each sublist has its own [ ]
The sublists have a , between them so without values it looks like [ [ ] , [ ] ,[ ] ]
The values in the sublists are all separated by , too just like they are in a normal (or 1D) list.