'''lecture_18_sublists.py
Demonstrate how to work with sublists
Oliver W. Layton
CS151: Computational Thinking: Visual Media
Fall 2020
'''

'''
Python allows us to store sublists: lists inside lists:
'''
digits = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
# Might be easier to see the "items" when written the following way:
# (but often not used because more effort to write)
digits = [
   [1, 2, 3],
   [4, 5, 6],
   [7, 8, 9]]

# What is the length of digits (number of items)?
print(len(digits))


# How do we access the second sublist (`[4, 5, 6]`)?
print(digits[1])


# How do we access the 1st two sublists `[[1, 2, 3], [4, 5, 6]]`?
print(digits[:2])

'''
Multiple indexing
'''
# How do we access/address the individual ints rather than the lists?
# Need multiple nexting notation: double set of square brackets
# Example: digits[0][1] takes the first item of the list of lists
# (a list), then from that sublist it takes the 2nd item (at index 1):
print(digits[0][2])

# When written like the following, you can think of a list of lists
# like a matrix or table: `digits[<row number>][column number>]`
digits = [
   [1, 2, 3],
   [4, 5, 6],
   [7, 8, 9]]