Añadir ejercicio 043-inheritance_and_polymorphism

exercises/043-inheritance_and_polymorphism/README.es.md

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+# `043` Inheritance and polymorphism
+
+Ahora que entendemos qué es una clase y algunas de sus características, hablemos sobre dos nuevos conceptos relacionados con las clases: herencia y polimorfismo. Considera el siguiente ejemplo:
+
+```py
+class HighSchoolStudent(Student):  # Agrega la clase padre dentro de los paréntesis
+    def __init__(self, name, age, grade, specialization):
+        super().__init__(name, age, grade)
+        self.specialization = specialization
+
+    def study(self, hours):
+        return f"{self.name} is a high school student specializing in {self.specialization} and is studying for {hours} hours for exams."
+
+# Creando una instancia de HighSchoolStudent
+high_school_student = HighSchoolStudent("John", 16, 85, "Science")
+print(high_school_student.introduce())  # Podemos llamar a este método gracias a la herencia
+print(high_school_student.study(4))  # Este método ha sido ligeramente modificado y ahora retorna un string diferente
+```
+
+Suponiendo que la clase `Student` del ejercicio anterior está definida justo encima de esta clase `HighSchoolStudent`, para heredar sus métodos y atributos, simplemente incluimos el nombre de la clase que queremos heredar (la clase padre) dentro de los paréntesis de la clase hija (`HighSchoolStudent`). Como puedes ver, ahora podemos usar el método `introduce` de la clase `Student` sin tener que codificarlo nuevamente, haciendo nuestro código más eficiente. Lo mismo se aplica a los atributos; no necesitamos redefinirlos.
+
+Además, tenemos la flexibilidad de agregar nuevos métodos exclusivamente para esta clase o incluso sobreescribir un método heredado si es necesario, como se demuestra en el método `study` que está ligeramente modificado con respecto a la clase `Student`; esto se llama **polimorfismo**.
+
+## 📝 Instrucciones:
+
+1. Crea una clase llamada `CollegeStudent` que herede de la clase `Student` ya definida.
+
+2. Agrega un nuevo atributo llamado `major` para representar la carrera que están estudiando.
+
+3. Modifica el método heredado `introduce` para retornar este string:
+
+```py
+"Hi there! I'm <name>, a college student majoring in <major>."
+```
+
+4. Agrega un nuevo método llamado `attend_lecture` que retorne el siguiente string:
+
+```py
+"<name> is attending a lecture for <major> students."
+```
+
+5. Crea una instancia de tu nueva clase y llama a cada uno de sus métodos. Ejecuta tu código para asegurarte de que funcione.
+
+
+## 💡 Pista:
+
++ Puede que hayas notado el uso de un nuevo método `super()`, que es necesario para heredar de una clase padre. Observa dónde se encuentra ubicado y lee más sobre él aquí: [Entendiendo super() en Python](https://realpython.com/python-super/).

exercises/043-inheritance_and_polymorphism/README.md

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+# `043` Inheritance and polymorphism
+
+Now that we understand what a class is and some of its characteristics, let's talk about two new concepts related to classes: inheritance and polymorphism. Consider the following example:
+
+```py
+class HighSchoolStudent(Student):  # Add the parent class inside the parenthesis
+    def __init__(self, name, age, grade, specialization):
+        super().__init__(name, age, grade)
+        self.specialization = specialization
+
+    def study(self, hours):
+        return f"{self.name} is a high school student specializing in {self.specialization} and is studying for {hours} hours for exams."
+
+# Creating an instance of HighSchoolStudent
+high_school_student = HighSchoolStudent("John", 16, 85, "Science")
+print(high_school_student.introduce())  # We can call this method thanks to inheritance 
+print(high_school_student.study(4))  # This method has been slightly modified and now it returns a different string
+```
+
+Assuming that the `Student` class from the previous exercise is coded just above this `HighSchoolStudent` class, to inherit its methods and attributes, we simply include the name of the class we want to inherit from (the parent class) inside the parentheses of the child class (`HighSchoolStudent`). As you can see, we can now use the `introduce` method from the `Student` class without having to code it again, making our code more efficient. The same applies to attributes; we don't need to redefine them.
+
+Additionally, we have the flexibility to add new methods exclusively for this class or even override an inherited method if needed, as demonstrated in the `study` method, which is slightly modified from the `Student` method; this is called **polymorphism**.
+
+## 📝 Instructions:
+
+1. Create a class called `CollegeStudent` which inherits from the already defined `Student` class.
+
+2. Add a new attribute called `major` to represent the major they are studying.
+
+3. Modify the inherited `introduce` method to return this string:
+
+```py
+"Hi there! I'm <name>, a college student majoring in <major>."
+```
+
+4. Add a new method called `attend_lecture` that returns the following string:
+
+```py
+"<name> is attending a lecture for <major> students."
+```
+
+5. Create an instance of your newly created class and call each of its methods. Execute your code to ensure it works.
+
+## 💡 Hint:
+
++ You may have noticed the use of a new method `super()` which is necessary for inheriting from a parent class. Take a look at where it is positioned and have a read about it: [Understanding Python's super()](https://realpython.com/python-super/).

exercises/043-inheritance_and_polymorphism/app.py

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+### DON'T modify this code ###
+
+class Student:
+    def __init__(self, name, age, grade):
+        self.name = name
+        self.age = age
+        self.grade = grade
+
+    def introduce(self):
+        return f"Hello! I am {self.name}, I am {self.age} years old, and my current grade is {self.grade}."
+
+    def study(self, hours):
+        return f"{self.name} is studying for {hours} hours."
+
+### DON'T modify the code above ###
+
+### ↓ Your code here ↓ ###

exercises/043-inheritance_and_polymorphism/solution.hide.py

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+### DON'T modify this code ###
+
+class Student:
+    def __init__(self, name, age, grade):
+        self.name = name
+        self.age = age
+        self.grade = grade
+
+    def introduce(self):
+        return f"Hello! I am {self.name}, I am {self.age} years old, and my current grade is {self.grade}."
+
+    def study(self, hours):
+        return f"{self.name} is studying for {hours} hours."
+
+### DON'T modify the code above ###
+
+### ↓ Your code here ↓ ###
+
+class CollegeStudent(Student):
+    def __init__(self, name, age, grade, major):
+        super().__init__(name, age, grade)
+        self.major = major
+
+    def introduce(self):
+        return f"Hi there! I'm {self.name}, a college student majoring in {self.major}."
+
+    def attend_lecture(self):
+        return f"{self.name} is attending a lecture for {self.major} students."
+
+
+college_student = CollegeStudent("Alice", 20, 90, "Computer Science")
+print(college_student.introduce())
+print(college_student.study(3))
+print(college_student.attend_lecture())

exercises/043-inheritance_and_polymorphism/test.py

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+import pytest
+from app import CollegeStudent
+
+@pytest.mark.it("The CollegeStudent class should exist")
+def test_college_student_class_exists():
+    try:
+        assert CollegeStudent
+    except AttributeError:
+        raise AttributeError("The class 'CollegeStudent' should exist in app.py")
+
+@pytest.mark.it("The CollegeStudent class includes the 'name' attribute")
+def test_college_student_has_name_attribute():
+    college_student = CollegeStudent("John", 21, 75, "Computer Science")
+    assert hasattr(college_student, "name")
+
+@pytest.mark.it("The CollegeStudent class includes the 'age' attribute")
+def test_college_student_has_age_attribute():
+    college_student = CollegeStudent("John", 21, 75, "Computer Science")
+    assert hasattr(college_student, "age")
+
+@pytest.mark.it("The CollegeStudent class includes the 'grade' attribute")
+def test_college_student_has_grade_attribute():
+    college_student = CollegeStudent("John", 21, 75, "Computer Science")
+    assert hasattr(college_student, "grade")
+
+@pytest.mark.it("The CollegeStudent class includes the 'major' attribute")
+def test_college_student_has_major_attribute():
+    college_student = CollegeStudent("John", 21, 75, "Computer Science")
+    assert hasattr(college_student, "major")
+
+@pytest.mark.it("The CollegeStudent class includes the 'introduce' method")
+def test_college_student_has_introduce_method():
+    college_student = CollegeStudent("Alice", 22, 90, "Computer Science")
+    assert hasattr(college_student, "introduce")
+
+@pytest.mark.it("The CollegeStudent class includes the 'study' method")
+def test_college_student_has_study_method():
+    college_student = CollegeStudent("John", 21, 75, "Computer Science")
+    assert hasattr(college_student, "study")    
+
+@pytest.mark.it("The CollegeStudent class includes the 'attend_lecture' method")
+def test_college_student_has_attend_lecture_method():
+    college_student = CollegeStudent("John", 21, 75, "Computer Science")
+    assert hasattr(college_student, "attend_lecture")
+
+@pytest.mark.it("The introduce method should return the expected string. Testing with different values")
+def test_college_student_introduce_method_returns_expected_string():
+    student1 = CollegeStudent("Alice", 22, 90, "Computer Science")
+    student2 = CollegeStudent("Bob", 19, 85, "Mathematics")
+    assert student1.introduce() == "Hi there! I'm Alice, a college student majoring in Computer Science."
+    assert student2.introduce() == "Hi there! I'm Bob, a college student majoring in Mathematics."
+
+@pytest.mark.it("The study method should return the expected string. Testing with different values")
+def test_college_student_study_method_returns_expected_string():
+    student1 = CollegeStudent("Eve", 20, 78, "Physics")
+    student2 = CollegeStudent("Charlie", 23, 88, "Chemistry")
+    assert student1.study(3) == "Eve is studying for 3 hours."
+    assert student2.study(2) == "Charlie is studying for 2 hours."
+
+@pytest.mark.it("The attend_lecture method should return the expected string. Testing with different values")
+def test_college_student_attend_lecture_method_returns_expected_string():
+    student1 = CollegeStudent("Eve", 20, 78, "Physics")
+    student2 = CollegeStudent("Charlie", 23, 88, "Chemistry")
+    assert student1.attend_lecture() == "Eve is attending a lecture for Physics students."
+    assert student2.attend_lecture() == "Charlie is attending a lecture for Chemistry students."
+