py-set-difference-operation

Set .difference() Operation ⬀

.difference()

The tool .difference() returns a set with all the elements from the set that are not in an iterable.

Sometimes the - operator is used in place of the .difference() tool, but it only operates on the set of elements in set.

Set is immutable to the .difference() operation (or the - operation).

>>> s = set("Hacker")
>>> print s.difference("Rank")
set(['c', 'r', 'e', 'H'])

>>> print s.difference(set(['R', 'a', 'n', 'k']))
set(['c', 'r', 'e', 'H'])

>>> print s.difference(['R', 'a', 'n', 'k'])
set(['c', 'r', 'e', 'H'])

>>> print s.difference(enumerate(['R', 'a', 'n', 'k']))
set(['a', 'c', 'r', 'e', 'H', 'k'])

>>> print s.difference({"Rank":1})
set(['a', 'c', 'e', 'H', 'k', 'r'])

>>> s - set("Rank")
set(['H', 'c', 'r', 'e'])

Task

Students of District College have a subscription to English and French newspapers. Some students have subscribed to only the English newspaper, some have subscribed to only the French newspaper, and some have subscribed to both newspapers.

You are given two sets of student roll numbers. One set has subscribed to the English newspaper, and one set has subscribed to the French newspaper. Your task is to find the total number of students who have subscribed to only English newspapers.

Task

The students of District College have subscriptions to English and French newspapers. Some students have subscribed only to English, some have subscribed to only French and some have subscribed to both newspapers.

You are given two sets of student roll numbers. One set has subscribed to the English newspaper, and the other set is subscribed to the French newspaper. The same student could be in both sets. Your task is to find the total number of students who have subscribed to at least one newspaper.

Input Format

• The first line contains an integer, n, the number of students who have subscribed to the English newspaper.
• The second line contains n space separated roll numbers of those students.
• The third line contains b, the number of students who have subscribed to the French newspaper.
• The fourth line contains b space separated roll numbers of those students.

Constraints

• 0 < Total number of students in college < 1000

Output Format

Output the total number of students who have at least one subscription.

Sample Input

9
1 2 3 4 5 6 7 8 9
9
10 1 2 3 11 21 55 6 8

Sample Output

4

Explanation

The roll numbers of students who only have English newspaper subscriptions are: 4, 5, 7 and 9.

Hence, the total is 4 students.