I’m trying to understand the diamond problem through the following code:
#implement Hybrid Inheritance
class University:
def __init__(self,univ_name):
self.univ_name=univ_name
def show_details(self):
print(f"University Name : {self.univ_name}")
class Course(University):
def __init__(self, univ_name,course_name):
super().__init__(univ_name)
self.course_name=course_name
def show_details(self):
super().show_details()
print(f"Course_name : {self.course_name}")
class Branch(University):
def __init__(self, univ_name, branch_name):
super().__init__(univ_name)
self.branch_name=branch_name
def show_details(self):
super().show_details()
print(f"Branch_name : {self.branch_name}")
class Student(Course,Branch):
def __init__(self, univ_name, course_name,branch_name):
Course.__init__(self,univ_name, course_name)
Branch.__init__(self,univ_name,branch_name)
def show_details(self):
Course.show_details(self)
Branch.show_details(self)
std_1=Student("UTL","Masters","CSE")
std_1.show_details()
When I run the code, I’m getting the following error:
Traceback (most recent call last):
File "AssignementsExercise_4.py", line 35, in <module>
std_1=Student("UTL","Masters","CSE")
File "AssignementsExercise_4.py", line 29, in __init__
Course.__init__(self,univ_name, course_name)
File "AssignementsExercise_4.py", line 11, in __init__
super().__init__(univ_name)
TypeError: __init__() missing 1 required positional argument: 'branch_name'
Is the above error due to the diamond problem, and how can it be resolved?
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6
You can get the __mro__ attribute (meaning method resolution order) to see the class hierarchy:
print(Student.__mro__)
(<class '__main__.Student'>, <class '__main__.Course'>, <class '__main__.Branch'>, <class '__main__.University'>, <class 'object'>)
So in the case of a student, the Course class is calling super().__init__ on the Branch class. This could be fixed by doing like what you did for the Student class and doing:
University.__init__(self, univ_name)
In the Branch and Course classes.
A better way to solve it would be to use composition:
A University has courses and branches. Courses have students. Branches have students:
class University:
def __init__(self, name):
self.name = name
self.courses: list[Course] = []
self.branches: list[Branch] = []
def add_course(self, course):
self.courses.append(course)
def add_branch(self, branch):
self.branches.append(branch)
def show_details(self):
print(f"University Name: {self.name}")
print("Courses Offered:")
for course in self.courses:
course.show_details()
print("Branches Available:")
for branch in self.branches:
branch.show_details()
class Course:
def __init__(self, name):
self.name = name
self.students = []
def show_details(self):
print(f"Course Name: {self.name}")
print("Students: ")
for student in self.students:
student.show_details()
def add_student(self, student):
self.students.append(student)
class Branch:
def __init__(self, name):
self.name = name
self.students: list[Student] = []
def show_details(self):
print(f"Branch Name: {self.name}")
print("Students: ")
for student in self.students:
student.show_details()
def add_student(self, student):
self.students.append(student)
class Student:
def __init__(self, name):
self.name = name
def show_details(self):
print(f"Student Name: {self.name}")
def main():
university = University("UTL")
course_masters = Course("Masters")
branch_cse = Branch("CSE")
university.add_course(course_masters)
university.add_branch(branch_cse)
student = Student("John Doe")
course_masters.add_student(student)
branch_cse.add_student(student)
university.show_details()
if __name__ == "__main__":
main()
Output:
University Name: UTL
Courses Offered:
Course Name: Masters
Students:
Student Name: John Doe
Branches Available:
Branch Name: CSE
Students:
Student Name: John Doe
You could restructure this for your usecase.
2