'''lecture_18_nested_loops.py
Demonstrate using nested lists
Oliver W. Layton
CS 151: Computational Thinking: Visual Media
Fall 2020
'''


'''
Visiting every item in a list with sublists
'''
# How can we access and replace every item in `digits`
# with 10 times the number?
digits = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# What is len(digits)?
# print(len(digits))

# If we loop thru, what type of data is digits[i]?
# for i in range(len(digits)):
#     print(digits[i])

# To visit each int, as we loop through the list,
# let's start looping thru the sublist and print each item.
# for i in range(len(digits)):
#     # inside "i" loop over sublists. Now we loop thru the SUBLIST digits[i] and get single items out
#     # digits[i] is a sublist — e.g. [1, 2, 3]
#     for j in range(len(digits[i])):
#         print(digits[i][j])

# Now let's tackle the problem of replacing each number with 10 times
# the amount.
for i in range(len(digits)):
    for j in range(len(digits[i])):
        digits[i][j] = 10*digits[i][j]

print(digits)

# What values do `i` and `j` take on while iterating thru the nested loop?
# Let's print the see
for i in range(len(digits)):
    for j in range(len(digits[i])):
        print('i =', i, ', j =', j)
    print('--Done with inner loop!--')