West Midlands | 26 March SDC | Iswat Bello | Sprint 5 | prep exercises for Object-Oriented Programming and Type safety

.gitignore

@@ -1 +1,3 @@
 node_modules
+.venv
+*.class

prep/classes_and_objects_exercise1.py

@@ -0,0 +1,17 @@
+class Person:
+    def __init__(self, name: str, age: int, preferred_operating_system: str):
+        self.name = name
+        self.age = age
+        self.preferred_operating_system = preferred_operating_system
+
+imran = Person("Imran", 22, "Ubuntu")
+print(imran.name)
+print(imran.address)
+
+eliza = Person("Eliza", 34, "Arch Linux")
+print(eliza.name)
+print(eliza.address)
+
+# Answer
+# The error returned after running mypy classes_and_objects_exercise1.py means that the Person class does not have an address attribute.
+# An instance of Person was created with name, age and preferred_operating_system only.

prep/classes_and_objects_exercise2.py

@@ -0,0 +1,22 @@
+class Person:
+    def __init__(self, name: str, age: int, preferred_operating_system: str):
+        self.name = name
+        self.age = age
+        self.preferred_operating_system = preferred_operating_system
+
+imran = Person("Imran", 22, "Ubuntu")
+print(imran.name)
+
+
+eliza = Person("Eliza", 34, "Arch Linux")
+print(eliza.name)
+
+def is_adult(person: Person) -> bool:
+    return person.age >= 18
+
+print(is_adult(imran))
+
+def is_adult_wrong_attribute(person: Person) -> bool:
+    return person.address
+
+print(is_adult_wrong_attribute(imran))

prep/dataclasses-exercise.py

@@ -0,0 +1,26 @@
+from datetime import date
+from dataclasses import dataclass
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    date_of_birth: date
+    preferred_operating_system: str
+
+    def is_adult(self) -> bool:
+        today = date.today()
+        age = today.year - self.date_of_birth.year
+
+        # Check if birthday has occurred this year
+        if (today.month, today.day) < (self.date_of_birth.month, self.date_of_birth.day):
+            age -= 1
+
+        return age >= 18
+
+imran = Person("Imran", date(2002, 5, 15), "Ubuntu")
+print(imran.name)
+print(imran.is_adult())
+
+eliza = Person("Eliza", date(1990, 3, 20), "Arch Linux")
+print(eliza.name)
+print(eliza.is_adult())

prep/enums-exercise.py

@@ -0,0 +1,73 @@
+from dataclasses import dataclass
+from enum import Enum
+from typing import List
+
+class OperatingSystem(Enum):
+    MACOS = "macOS"
+    ARCH = "Arch Linux"
+    UBUNTU = "Ubuntu"
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    age: int
+    preferred_operating_system: OperatingSystem
+
+
+@dataclass(frozen=True)
+class Laptop:
+    id: int
+    manufacturer: str
+    model: str
+    screen_size_in_inches: float
+    operating_system: OperatingSystem
+
+
+def find_possible_laptops(laptops: List[Laptop], person: Person) -> List[Laptop]:
+    possible_laptops = []
+    for laptop in laptops:
+        if laptop.operating_system == person.preferred_operating_system:
+            possible_laptops.append(laptop)
+    return possible_laptops
+
+
+def create_person_from_input(laptops: List[Laptop]) -> None:
+    name = input("Enter person's name: ")
+    age = int(input("Enter person's age: "))
+
+    print("Available operating systems:")
+    for os in OperatingSystem:
+        print(f"  {os.name}: {os.value}")
+
+    os_choice = input("Enter preferred operating system (MACOS/ARCH/UBUNTU): ").upper()
+
+    try:
+        preferred_os = OperatingSystem[os_choice]
+    except KeyError:
+        print("Invalid operating system choice!")
+        return
+
+    person = Person(name=name, age=age, preferred_operating_system=preferred_os)
+    possible_laptops = find_possible_laptops(laptops, person)
+
+    print(f"\nPossible laptops for {person.name}: {possible_laptops}")
+    print(f"The library has {len(possible_laptops)} laptop(s) with {preferred_os.value}")
+
+laptops = [
+    Laptop(id=1, manufacturer="Dell", model="XPS", screen_size_in_inches=13, operating_system=OperatingSystem.ARCH),
+    Laptop(id=2, manufacturer="Dell", model="XPS", screen_size_in_inches=15, operating_system=OperatingSystem.UBUNTU),
+    Laptop(id=3, manufacturer="Dell", model="XPS", screen_size_in_inches=15, operating_system=OperatingSystem.UBUNTU),
+    Laptop(id=4, manufacturer="Apple", model="macBook", screen_size_in_inches=13, operating_system=OperatingSystem.MACOS),
+]
+
+people = [
+    Person(name="Imran", age=22, preferred_operating_system=OperatingSystem.UBUNTU),
+    Person(name="Eliza", age=34, preferred_operating_system=OperatingSystem.ARCH),
+]
+
+for person in people:
+    possible_laptops = find_possible_laptops(laptops, person)
+    print(f"Possible laptops for {person.name}: {possible_laptops}")
+
+print("\n--- Create a new person ---")
+create_person_from_input(laptops)

prep/generics-exercise1.py

@@ -0,0 +1,30 @@
+from dataclasses import dataclass
+from typing import List
+from datetime import date
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    date_of_birth: date
+    children: List["Person"]
+
+    def age(self) -> int:
+        today = date.today()
+        age = today.year - self.date_of_birth.year
+        if (today.month, today.day) < (self.date_of_birth.month, self.date_of_birth.day):
+            age -= 1
+        return age
+
+fatma = Person(name="Fatma", date_of_birth=date(2015, 7, 22), children=[])
+aisha = Person(name="Aisha", date_of_birth=date(2018, 3, 10), children=[])
+
+imran = Person(name="Imran", date_of_birth=date(1985, 5, 15), children=[fatma, aisha])
+
+def print_family_tree(person: Person) -> None:
+    print(person.name)
+    for child in person.children:
+        print(f"- {child.name} ({child.age()})")
+
+print_family_tree(imran)
+
+

prep/inheritance-exercise.py

@@ -0,0 +1,37 @@
+class Parent:
+    def __init__(self, first_name: str, last_name: str):
+        self.first_name = first_name
+        self.last_name = last_name
+
+    def get_name(self) -> str:
+        return f"{self.first_name} {self.last_name}"
+
+
+class Child(Parent):
+    def __init__(self, first_name: str, last_name: str):
+        super().__init__(first_name, last_name)
+        self.previous_last_names = []
+
+    def change_last_name(self, last_name) -> None:
+        self.previous_last_names.append(self.last_name)
+        self.last_name = last_name
+
+    def get_full_name(self) -> str:
+        suffix = ""
+        if len(self.previous_last_names) > 0:
+            suffix = f" (née {self.previous_last_names[0]})"
+        return f"{self.first_name} {self.last_name}{suffix}"
+
+person1 = Child("Elizaveta", "Alekseeva")
+print(person1.get_name())
+#print(person1.get_full_name())
+#person1.change_last_name("Tyurina")
+print(person1.get_name())
+#print(person1.get_full_name())
+
+person2 = Parent("Elizaveta", "Alekseeva")
+print(person2.get_name())
+#print(person2.get_full_name())
+#person2.change_last_name("Tyurina")
+print(person2.get_name())
+#print(person2.get_full_name())

prep/methods-exercise1.md

@@ -0,0 +1,27 @@
+Here are the advantages of using methods instead of free functions:
+
+1. **Organization** - Methods are part of a class, so related code is organized together in one place.
+
+2. **Access to object data** - Methods can directly access the object's attributes (like `person.age`). Free functions need the object passed as a parameter.
+
+3. **Clearer intent** - When you see `person.is_adult()`, it's clear that you're asking "is this person an adult?" instead of `is_adult(person)`.
+
+4. **Less parameter passing** - Methods use `self` automatically, so you don't need to pass the object as a parameter every time.
+
+5. **Better grouping** - All actions for a `Person` are grouped together inside the `Person` class, not scattered around your code.
+
+6. **Easier to maintain** - If you need to change how `is_adult()` works, you only need to update the method in one place inside the class.
+
+7. **More readable** - `imran.is_adult()` is easier to read and understand than `is_adult(imran)`.
+
+**Example comparison:**
+
+```python
+# Free function (current approach)
+print(is_adult(imran))
+
+# Method (better approach)
+print(imran.is_adult())
+```
+
+The method version is clearer and more organized!

prep/methods-exercise2.py

@@ -0,0 +1,25 @@
+from datetime import date
+
+class Person:
+    def __init__(self, name: str, date_of_birth: date, preferred_operating_system: str):
+        self.name = name
+        self.date_of_birth = date_of_birth
+        self.preferred_operating_system = preferred_operating_system
+
+    def is_adult(self) -> bool:
+        today = date.today()
+        age = today.year - self.date_of_birth.year
+
+        # Check if birthday has occurred this year
+        if (today.month, today.day) < (self.date_of_birth.month, self.date_of_birth.day):
+            age -= 1
+
+        return age >= 18
+
+imran = Person("Imran", date(2002, 5, 15), "Ubuntu")
+print(imran.name)
+print(imran.is_adult())
+
+eliza = Person("Eliza", date(1990, 3, 20), "Arch Linux")
+print(eliza.name)
+print(eliza.is_adult())

prep/type-guided-refactoring-exercise.py

@@ -0,0 +1,42 @@
+from dataclasses import dataclass
+from typing import List
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    age: int
+    preferred_operating_systems: List[str]
+
+
+@dataclass(frozen=True)
+class Laptop:
+    id: int
+    manufacturer: str
+    model: str
+    screen_size_in_inches: float
+    operating_system: str
+
+
+def find_possible_laptops(laptops: List[Laptop], person: Person) -> List[Laptop]:
+    possible_laptops = []
+    for laptop in laptops:
+        if laptop.operating_system in person.preferred_operating_systems:
+            possible_laptops.append(laptop)
+    return possible_laptops
+
+
+people = [
+    Person(name="Imran", age=22, preferred_operating_systems=["Ubuntu", "Arch Linux"]),
+    Person(name="Eliza", age=34, preferred_operating_systems=["Arch Linux"]),
+]
+
+laptops = [
+    Laptop(id=1, manufacturer="Dell", model="XPS", screen_size_in_inches=13, operating_system="Arch Linux"),
+    Laptop(id=2, manufacturer="Dell", model="XPS", screen_size_in_inches=15, operating_system="Ubuntu"),
+    Laptop(id=3, manufacturer="Dell", model="XPS", screen_size_in_inches=15, operating_system="ubuntu"),
+    Laptop(id=4, manufacturer="Apple", model="macBook", screen_size_in_inches=13, operating_system="macOS"),
+]
+
+for person in people:
+    possible_laptops = find_possible_laptops(laptops, person)
+    print(f"Possible laptops for {person.name}: {possible_laptops}")

prep/type_checking_with_mypy.py

@@ -0,0 +1,30 @@
+def open_account(balances: dict[str, int], name: str, amount: int) -> None:
+    balances[name] = amount
+
+def sum_balances(accounts: dict[str, int]) -> int:
+    total = 0
+    for name, pence in accounts.items():
+        print(f"{name} had balance {pence}")
+        total += pence
+    return total
+
+def format_pence_as_string(total_pence: int) -> str:
+    if total_pence < 100:
+        return f"{total_pence}p"
+    pounds = int(total_pence / 100)
+    pence = total_pence % 100
+    return f"£{pounds}.{pence:02d}"
+
+balances: dict[str, int] = {
+    "Sima": 700,
+    "Linn": 545,
+    "Georg": 831,
+}
+
+open_account(balances, "Tobi", 913)
+open_account(balances, "Olya", 713)
+
+total_pence: int = sum_balances(balances)
+total_string: str = format_pence_as_string(total_pence)
+
+print(f"The bank accounts total {total_string}")

prep/why_we_use_types_exercise1.py

@@ -0,0 +1,20 @@
+def half(value):
+    return value / 2 
+
+def double(value):
+    return value * 2 
+
+def second(value):
+    return value[1]
+
+
+print(double("22"))
+
+# Question
+# Predict what double("22") will do. Then run the code and check. Did it do what you expected? Why did it return the value it did?
+
+# Answer
+# The function double("22") will return "2222".
+# When I ran the program, it returned what I expected.
+# The return value is "2222" because the argument is a string, so the * operator duplicates the string instead of 
+# multiplying a number. Python repeats the string twice: "22" + "22" = "2222".

prep/why_we_use_types_exercise2.py

@@ -0,0 +1,14 @@
+# Question
+
+def double(number):
+    return number * 3
+
+print(double(10))
+
+# Read the above code and write down what the bug is. How would you fix it?
+
+
+# Answer
+# The bug: The function multiplies the number by 3 instead of 2, which contradicts its name.
+
+# Proposed fix: We can either change the function implementation so that it returns number * 2 or we change the function name to 'triple'