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Merge pull request #62 from josemoracard/jose11--add-3-class-exercises
Añadir ejercicio 043-inheritance_and_polymorphism
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# `043` Inheritance and polymorphism
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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:
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```py
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class HighSchoolStudent(Student): # Agrega la clase padre dentro de los paréntesis
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def __init__(self, name, age, grade, specialization):
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super().__init__(name, age, grade)
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self.specialization = specialization
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def study(self, hours):
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return f"{self.name} is a high school student specializing in {self.specialization} and is studying for {hours} hours for exams."
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# Creando una instancia de HighSchoolStudent
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high_school_student = HighSchoolStudent("John", 16, 85, "Science")
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print(high_school_student.introduce()) # Podemos llamar a este método gracias a la herencia
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print(high_school_student.study(4)) # Este método ha sido ligeramente modificado y ahora retorna un string diferente
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```
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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.
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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**.
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## 📝 Instrucciones:
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1. Crea una clase llamada `CollegeStudent` que herede de la clase `Student` ya definida.
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2. Agrega un nuevo atributo llamado `major` para representar la carrera que están estudiando.
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3. Modifica el método heredado `introduce` para retornar este string:
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```py
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"Hi there! I'm <name>, a college student majoring in <major>."
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```
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4. Agrega un nuevo método llamado `attend_lecture` que retorne el siguiente string:
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```py
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"<name> is attending a lecture for <major> students."
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```
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5. Crea una instancia de tu nueva clase y llama a cada uno de sus métodos. Ejecuta tu código para asegurarte de que funcione.
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## 💡 Pista:
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+ 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/).
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# `043` Inheritance and polymorphism
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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:
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```py
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class HighSchoolStudent(Student): # Add the parent class inside the parenthesis
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def __init__(self, name, age, grade, specialization):
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super().__init__(name, age, grade)
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self.specialization = specialization
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def study(self, hours):
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return f"{self.name} is a high school student specializing in {self.specialization} and is studying for {hours} hours for exams."
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# Creating an instance of HighSchoolStudent
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high_school_student = HighSchoolStudent("John", 16, 85, "Science")
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print(high_school_student.introduce()) # We can call this method thanks to inheritance
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print(high_school_student.study(4)) # This method has been slightly modified and now it returns a different string
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```
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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.
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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**.
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## 📝 Instructions:
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1. Create a class called `CollegeStudent` which inherits from the already defined `Student` class.
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2. Add a new attribute called `major` to represent the major they are studying.
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3. Modify the inherited `introduce` method to return this string:
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```py
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"Hi there! I'm <name>, a college student majoring in <major>."
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```
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4. Add a new method called `attend_lecture` that returns the following string:
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```py
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"<name> is attending a lecture for <major> students."
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```
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5. Create an instance of your newly created class and call each of its methods. Execute your code to ensure it works.
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## 💡 Hint:
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+ 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/).
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### DON'T modify this code ###
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class Student:
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def __init__(self, name, age, grade):
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self.name = name
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self.age = age
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self.grade = grade
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def introduce(self):
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return f"Hello! I am {self.name}, I am {self.age} years old, and my current grade is {self.grade}."
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def study(self, hours):
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return f"{self.name} is studying for {hours} hours."
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### DON'T modify the code above ###
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### ↓ Your code here ↓ ###
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### DON'T modify this code ###
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class Student:
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def __init__(self, name, age, grade):
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self.name = name
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self.age = age
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self.grade = grade
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def introduce(self):
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return f"Hello! I am {self.name}, I am {self.age} years old, and my current grade is {self.grade}."
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def study(self, hours):
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return f"{self.name} is studying for {hours} hours."
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### DON'T modify the code above ###
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### ↓ Your code here ↓ ###
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class CollegeStudent(Student):
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def __init__(self, name, age, grade, major):
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super().__init__(name, age, grade)
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self.major = major
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def introduce(self):
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return f"Hi there! I'm {self.name}, a college student majoring in {self.major}."
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def attend_lecture(self):
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return f"{self.name} is attending a lecture for {self.major} students."
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college_student = CollegeStudent("Alice", 20, 90, "Computer Science")
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print(college_student.introduce())
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print(college_student.study(3))
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print(college_student.attend_lecture())
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import pytest
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from app import CollegeStudent
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@pytest.mark.it("The CollegeStudent class should exist")
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def test_college_student_class_exists():
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try:
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assert CollegeStudent
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except AttributeError:
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raise AttributeError("The class 'CollegeStudent' should exist in app.py")
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@pytest.mark.it("The CollegeStudent class includes the 'name' attribute")
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def test_college_student_has_name_attribute():
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college_student = CollegeStudent("John", 21, 75, "Computer Science")
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assert hasattr(college_student, "name")
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@pytest.mark.it("The CollegeStudent class includes the 'age' attribute")
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def test_college_student_has_age_attribute():
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college_student = CollegeStudent("John", 21, 75, "Computer Science")
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assert hasattr(college_student, "age")
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@pytest.mark.it("The CollegeStudent class includes the 'grade' attribute")
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def test_college_student_has_grade_attribute():
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college_student = CollegeStudent("John", 21, 75, "Computer Science")
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assert hasattr(college_student, "grade")
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@pytest.mark.it("The CollegeStudent class includes the 'major' attribute")
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def test_college_student_has_major_attribute():
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college_student = CollegeStudent("John", 21, 75, "Computer Science")
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assert hasattr(college_student, "major")
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@pytest.mark.it("The CollegeStudent class includes the 'introduce' method")
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def test_college_student_has_introduce_method():
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college_student = CollegeStudent("Alice", 22, 90, "Computer Science")
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assert hasattr(college_student, "introduce")
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@pytest.mark.it("The CollegeStudent class includes the 'study' method")
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def test_college_student_has_study_method():
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college_student = CollegeStudent("John", 21, 75, "Computer Science")
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assert hasattr(college_student, "study")
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@pytest.mark.it("The CollegeStudent class includes the 'attend_lecture' method")
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def test_college_student_has_attend_lecture_method():
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college_student = CollegeStudent("John", 21, 75, "Computer Science")
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assert hasattr(college_student, "attend_lecture")
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@pytest.mark.it("The introduce method should return the expected string. Testing with different values")
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def test_college_student_introduce_method_returns_expected_string():
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student1 = CollegeStudent("Alice", 22, 90, "Computer Science")
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student2 = CollegeStudent("Bob", 19, 85, "Mathematics")
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assert student1.introduce() == "Hi there! I'm Alice, a college student majoring in Computer Science."
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assert student2.introduce() == "Hi there! I'm Bob, a college student majoring in Mathematics."
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@pytest.mark.it("The study method should return the expected string. Testing with different values")
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def test_college_student_study_method_returns_expected_string():
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student1 = CollegeStudent("Eve", 20, 78, "Physics")
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student2 = CollegeStudent("Charlie", 23, 88, "Chemistry")
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assert student1.study(3) == "Eve is studying for 3 hours."
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assert student2.study(2) == "Charlie is studying for 2 hours."
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@pytest.mark.it("The attend_lecture method should return the expected string. Testing with different values")
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def test_college_student_attend_lecture_method_returns_expected_string():
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student1 = CollegeStudent("Eve", 20, 78, "Physics")
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student2 = CollegeStudent("Charlie", 23, 88, "Chemistry")
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assert student1.attend_lecture() == "Eve is attending a lecture for Physics students."
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assert student2.attend_lecture() == "Charlie is attending a lecture for Chemistry students."
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