def main():
Course1=Course('Data Structures')
Course2=Course('Database System')
Course1.addStudent('Peter Wang')
Course1.addStudent('Brian Li')
Course1.addStudent('Anne Wu')
Course2.addStudent('Peter Sun')
Course2.addStudent('Steve Cai')
print ('number of students in Course1: ', Course1.getNumOfStudents())
students=Course1.getStudents()
for student in students:
print (student,end=', ')
print ('\nnumber of students in Course2: ',Course2.getNumOfStudents())
