"""
Ex. 2.15 from "A primer on...",
Index a nested list and check the result. 
"""


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 i objects of the outer loop 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
"""