"""
Ex. 2.15 from "A primer on...",
Index a nested list and check the result. This exercise
was not done in the lecture but is useful to do on
your own as a quick check that you understand nested lists
"""


q = [['a', 'b', 'c'], ['d', 'e', 'f'], ['g', 'h']]

#a)
print(q[0][0]) #the letter a, first element in first list  
print(q[1])    #the list ['d', 'e', 'f'], the second element of the outer list
print(q[-1][-1]) #the last element h, the last element of the last list
print(q[1][0])  #the 'd' element, q[1] gives the second list, q[1][0] gives its first element
print(q[-1][-2])  #q[-1] gives the last list, q[-1][-2] gives the second-to-last element of this list, i.e., 'g'

#b) A nested for loop traverses all elements:
for i in q:
    for j in range(len(i)):
        print(i[j])

"""
Here, the objects are of type list, since they are the elements of the outer list q. 
The inner loop is constructed differently, using range(...) and indexing, 
so the j objects are integers. The printed values i[j] have type str.
"""

"""
Terminal> python index_nested_list.py 
a
['d', 'e', 'f']
h
d
g
a
b
c
d
e
f
g
h
"""