"""
Inconsistent behavior of set operators in Python 3.5.2.
- Using set.intersection generally throws a TypeError exception
  if its inputs include something that is not a set. However, it correctly finds
  the intersection between a set and a tuple when the first input is a set and
  the second is a tuple.
- Similar behavior occurs for multiple inputs, inputs that are lists or dicts
  (dict uses keys), and for other operators such as set.difference and
  set.union.
- The equivalent operators (&, -, |) do not allow any non-set inputs.

It appears that set.intersection, set.union, etc. only checks if its first input
is a set. If so, other iterable objects can be used and a correct result is
returned.
"""

# Exception when set.intersection sees inputs of tuple, set.

my_set = {1, 2, 3}
my_tuple = (2, 3, 4)
my_other_tuple = (3, 4, 5)
my_list = [2, 3, 4]
my_dict = {2: "b", 3: "c", 4: "d"}

print("My set:         {}".format(my_set))
print("My tuple:       {}".format(my_tuple))
print("My other tuple: {}".format(my_other_tuple))
print("My list:        {}".format(my_list))
print("My dict:        {}".format(my_dict))
print()

# Behavior using intersection.
print("Behavior using intersection:")

print("tuple & set: ", end="")  # raises TypeError exception.
try:
    print(my_tuple & my_set)
except TypeError:
    print("TypeError exception raised.")

print("set & tuple: ", end="")  # raises TypeError exception.
try:
    print(my_set & my_tuple)
except TypeError:
    print("TypeError exception raised.")

print("set.intersection(tuple, set):  ", end="")  # raises TypeError exception.
try:
    print(set.intersection(my_tuple, my_set))
except TypeError:
    print("TypeError exception raised.")

print("set.intersection(set, tuple): ", end="")  # returns valid intersection.
try:
    print(set.intersection(my_set, my_tuple))
except TypeError:
    print("TypeError exception raised.")


# Similar behavior using union and difference.
print("\nSimilar behavior using union and difference:")

print("set.union(tuple, set):  ", end="")  # raises TypeError exception.
try:
    print(set.union(my_tuple, my_set))
except TypeError:
    print("TypeError exception raised.")

print("set.union(set, tuple): ", end="")  # returns valid intersection.
try:
    print(set.union(my_set, my_tuple))
except TypeError:
    print("TypeError exception raised.")

print("set.difference(tuple, set):  ", end="")    # raises TypeError exception.
try:
    print(set.difference(my_tuple, my_set))
except TypeError:
    print("TypeError exception raised.")

print("set.difference(set, tuple): ", end="")  # returns valid intersection.
try:
    print(set.difference(my_set, my_tuple))
except TypeError:
    print("TypeError exception raised.")


# Behavior using 3 inputs to intersection.
print("\nBehavior using 3 inputs to intersection:")

print("set.intersection(tuple, set, tuple):  ", end="")
# Raises TypeError exception.
try:
    print(set.intersection(my_tuple, my_set, my_other_tuple))
except TypeError:
    print("TypeError exception raised.")

print("set.intersection(tuple, tuple, set):  ", end="")
# Raises TypeError exception.
try:
    print(set.intersection(my_tuple, my_other_tuple, my_set))
except TypeError:
    print("TypeError exception raised.")

print("set.intersection(set, tuple, tuple): ", end="")
# Returns valid intersection.
try:
    print(set.intersection(my_set, my_tuple, my_other_tuple))
except TypeError:
    print("TypeError exception raised.")


# Behavior using list and dict.
print("\nBehavior using list and dict:")

print("set.intersection(list, set):  ", end="")  # raises TypeError exception.
try:
    print(set.intersection(my_list, my_set))
except TypeError:
    print("TypeError exception raised.")

print("set.intersection(set, list): ", end="")  # returns valid intersection.
try:
    print(set.intersection(my_set, my_list))
except TypeError:
    print("TypeError exception raised.")

print("set.intersection(dict, set):  ", end="")  # raises TypeError exception.
try:
    print(set.intersection(my_dict, my_set))
except TypeError:
    print("TypeError exception raised.")

print("set.intersection(set, dict): ", end="")  # returns valid intersection.
try:
    print(set.intersection(my_set, my_dict))
except TypeError:
    print("TypeError exception raised.")