deep_reverse.py

# Question 9: Deep Reverse
# Define a procedure, deep_reverse, that takes as input a list,
# and returns a new list that is the deep reverse of the input list.
# This means it reverses all the elements in the list, and if any
# of those elements are lists themselves, reverses all the elements
# in the inner list, all the way down.

# Note: The procedure must not change the input list.

# The procedure is_list below is from Homework 6. It returns True if
# p is a list and False if it is not.

def is_list(p):
    return isinstance(p, list)


def deep_reverse(old_list):
    new_list = []
    for p in old_list:
        if isinstance(p, list):
            new_list = [deep_reverse(p)] + new_list
        else:
            new_list = [p] + new_list
    return new_list


# For example,

p = [1, [2, 3, [4, [5, 6]]]]
print deep_reverse(p)
# >>> [[[[6, 5], 4], 3, 2], 1]
print p
# >>> [1, [2, 3, [4, [5, 6]]]]

q = [1, [2, 3], 4, [5, 6]]
print deep_reverse(q)
# >>> [ [6,5], 4, [3, 2], 1]
print q
# >>> [1, [2,3], 4, [5,6]]