Add lesson 4

src/Lesson_4/lesson.py

@@ -0,0 +1,76 @@
+from abc import ABC, abstractmethod
+
+
+class Printable(ABC):
+    @abstractmethod
+    def print_info(self) -> None:
+        pass
+
+
+class Book(Printable):
+    def __init__(
+        self,
+        title: str,
+        year: int,
+        author: str,
+    ) -> None:
+        self.title = title
+        self.year = year
+        self.author = author
+
+    def print_info(self) -> None:
+        print(self)
+
+    def info(self) -> str:
+        return 'Книга "{}", автора: {}, {} года.'.format(
+            self.title,
+            self.author,
+            self.year,
+        )
+
+    @classmethod
+    def from_string(cls, string: str):
+        title, year, author = string.split(";")
+        return cls(title, int(year), author)
+
+    @property
+    def age(self) -> int:
+        return self.year
+
+    @age.setter
+    def age(self, value: int):
+        self.year = value
+
+    def __str__(self) -> str:
+        return self.info()
+
+    def __eq__(self, other) -> bool:
+        return isinstance(other, Book) and self.author == other.author
+
+
+class EBook(Book):
+    def __init__(
+        self, title: str, year: int, author: str, format_: str
+    ) -> str:
+        super().__init__(title, year, author)
+        self.format = format_
+
+    def info(self) -> str:
+        return 'Электронная книга "{}", автора: {}, {} года.'.format(
+            self.title,
+            self.author,
+            self.year,
+        )
+
+    @classmethod
+    def from_string(cls, string: str):
+        title, year, author, format_ = string.split(";")
+        return cls(title, int(year), author, format_)
+
+
+book = Book.from_string("Новый Заголовок;2021;Новый автор")
+print(book)
+book.print_info()
+
+ebook = EBook.from_string("Новый Заголовок;2021;Новый автор;epub")
+print(ebook)