London | July SDC | Ali Qassab | Sprint 4 | Prep exercises

prep-exercises/.gitignore

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+# Virtual Environment
+venv/
+env/
+ENV/
+
+# Python cache
+__pycache__/
+*.pyc
+*.pyo
+*.pyd
+
+# mypy cache
+.mypy_cache/
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+
+# OS
+.DS_Store
+

prep-exercises/classes_and_objects.py

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+class Person:
+    def __init__(self, name: str, age: int, preferred_operating_system: str, address: str):
+        self.name = name
+        self.age = age
+        self.preferred_operating_system = preferred_operating_system
+        self.address = address
+
+    def is_adult(self) -> bool:
+        return self.age >= 18
+
+
+imran = Person("Imran", 22, "Ubuntu", "123 Main St")
+print(imran.name)
+print(imran.address)
+print(imran.is_adult())
+
+eliza = Person("Eliza", 34, "Arch Linux", "456 Oak Ave")
+print(eliza.name)
+print(eliza.address)
+
+
+def get_address(person: Person) -> str:
+    return person.address
+
+print(get_address(imran))

prep-exercises/dataclasses_exercise.py

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+from dataclasses import dataclass
+from datetime import date
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    date_of_birth: date
+    preferred_operating_system: str
+
+    def is_adult(self) -> bool:
+        current_date = date.today()
+        age = current_date.year - self.date_of_birth.year - (
+            (current_date.month, current_date.day) < (self.date_of_birth.month, self.date_of_birth.day)
+        )
+        return age >= 18
+
+# Example usage:
+imran = Person("Imran", date(2001, 5, 15), "Ubuntu")
+print(imran)
+print(imran.is_adult())
+
+eliza = Person("Eliza", date(1990, 3, 20), "Arch Linux")
+print(eliza)
+print(eliza.is_adult())
+

prep-exercises/enums_exercise.py

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+from dataclasses import dataclass
+from enum import Enum
+
+class OperatingSystem(Enum):
+    MACOS = "macOS"
+    UBUNTU = "Ubuntu"
+    ARCH = "Arch Linux"
+
+@dataclass
+class Laptop:
+    id: int
+    manufacturer: str
+    model: str
+    screen_size_in_inches: float
+    operating_system: OperatingSystem
+
+laptops = [
+    Laptop(id=1, manufacturer="Lenovo", model="ThinkPad", screen_size_in_inches=14, operating_system=OperatingSystem.ARCH),
+    Laptop(id=2, manufacturer="HP", model="Pavilion", screen_size_in_inches=15.6, operating_system=OperatingSystem.UBUNTU),
+    Laptop(id=3, manufacturer="Asus", model="ZenBook", screen_size_in_inches=13.3, operating_system=OperatingSystem.UBUNTU),
+    Laptop(id=4, manufacturer="Apple", model="MacBook Air", screen_size_in_inches=13, operating_system=OperatingSystem.MACOS),
+]
+
+@dataclass
+class Person:
+    name: str
+    age: int
+    preferred_operating_system: OperatingSystem
+
+
+name = input('Please enter your name: ')
+
+age_input = input('Please enter your age: ')
+try:
+    age = int(age_input)
+except ValueError:
+    print(f"Error: '{age_input}' is not a valid age. Please enter a number.")
+    exit()
+
+preferred_os_input = input('Please enter your preferred operating system: ')
+try:
+    preferred_operating_system = OperatingSystem(preferred_os_input)
+except ValueError:
+    available_options = ', '.join([os.value for os in OperatingSystem])
+    print(f"Error: '{preferred_os_input}' is not available. Please choose from: {available_options}")
+    exit()
+
+
+person = Person(name=name, age=age, preferred_operating_system=preferred_operating_system)
+
+
+number_of_available_laptops = sum(
+    1 for laptop in laptops if laptop.operating_system == person.preferred_operating_system
+)
+
+def offer_laptop_to_user() -> None:
+    offer = input('Would you like a laptop with this OS (yes / no) ? ')
+    if offer.lower() == "y" or offer.lower() == "yes":
+        print('Great! Please come on monday next week to collect your laptop')
+    else:
+        print('No problem. See you later.')
+
+if number_of_available_laptops == 1:
+    print(f'There is {number_of_available_laptops} laptop available with your preferred operating system.')
+    offer_laptop_to_user()
+elif number_of_available_laptops > 1:
+    print(f'There are {number_of_available_laptops} laptops available with your preferred operating system.')
+    offer_laptop_to_user()
+else:
+    print('There are no laptops available with your preferred operating system.')

prep-exercises/generics.py

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+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:
+        current_date = date.today()
+        age = current_date.year - self.date_of_birth.year - (
+            (current_date.month, current_date.day) < (self.date_of_birth.month, self.date_of_birth.day)
+        )
+        return age
+
+# Calculate dates of birth based on current age
+def years_ago(years: int) -> date:
+    today = date.today()
+    try:
+        return date(today.year - years, today.month, today.day)
+    except ValueError:  # Handle leap year edge case (Feb 29)
+        return date(today.year - years, today.month, today.day - 1)
+
+sara = Person(name="Sara", date_of_birth=years_ago(5), children=[])
+ahmed = Person(name="Ahmed", date_of_birth=years_ago(8), children=[])
+
+ali = Person(name="Ali", date_of_birth=years_ago(28), children=[sara])
+aya = Person(name="Aya", date_of_birth=years_ago(32), children=[ahmed])
+
+imran = Person(name="Imran", date_of_birth=years_ago(55), children=[ali, aya])
+
+def print_family_tree(person: Person) -> None:
+    print(f"{person.name} ({person.age()})")
+    for child in person.children:
+        print(f"  - {child.name} ({child.age()})")
+        for grandchild in child.children:
+            print(f"    - {grandchild.name} ({grandchild.age()})")
+
+def count_family_members(person: Person) -> int:
+    count = 1
+    for child in person.children:
+        count += count_family_members(child)
+    return count
+
+print_family_tree(imran)
+print(f"\nTotal family members: {count_family_members(imran)}")

prep-exercises/inheritance.py

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+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: list[str] = []
+
+    def change_last_name(self, last_name: str) -> 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}"
+
+
+print("Creating Child instance:")
+person1 = Child("Sarah", "Johnson")
+print(f"Name: {person1.get_name()}")
+print(f"Full name: {person1.get_full_name()}")
+
+print("\nChanging last name to Smith:")
+person1.change_last_name("Smith")
+print(f"Name: {person1.get_name()}")
+print(f"Full name: {person1.get_full_name()}")
+
+print("\nCreating Parent instance:")
+person2 = Parent("Emma", "Wilson")
+print(f"Name: {person2.get_name()}")
+
+# person2.change_last_name("Brown")  # Error: Parent doesn't have change_last_name method

prep-exercises/methods.py

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+from datetime import date
+
+class Person:
+    def __init__(self, name: str, DoB: date, preferred_operating_system: str):
+        self.name = name
+        self.DoB = DoB
+        self.preferred_operating_system = preferred_operating_system
+
+    def is_adult(self) -> bool:
+        current_date = date.today()
+        age = current_date.year - self.DoB.year - (
+            (current_date.month, current_date.day) < (self.DoB.month, self.DoB.day)
+        )
+        return age >= 18
+
+
+
+eliza = Person("Eliza", date(2010, 5, 15), "Arch Linux")
+print(f"{eliza.name} is adult: {eliza.is_adult()}")
+
+sara = Person("Sara", date(1995, 12, 20), "macOS")
+print(f"{sara.name} is adult: {sara.is_adult()}")

prep-exercises/requirements.txt

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+mypy==1.18.2

prep-exercises/type_checking_with_mypy.py

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+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,
+}
+
+# Bugs fixed:
+# 1. Added balances as first argument
+# 2. Converted amounts to pence (int)
+# 3. Fixed function name typo
+open_account(balances, "Tobi", 913)
+open_account(balances, "Olya", 713)
+
+total_pence = sum_balances(balances)
+total_string = format_pence_as_string(total_pence)
+
+print(f"The bank accounts total {total_string}")

prep-exercises/type_guided_refactorings.py

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+from dataclasses import dataclass
+from typing import Optional
+
+# Before refactoring - unclear types
+def process_user_data(data):
+    name = data[0]
+    age = data[1]
+    email = data[2] if len(data) > 2 else None
+
+    if age < 18:
+        return None
+
+    return f"{name} ({age}): {email or 'no email'}"
+
+
+# After refactoring - clear types
+@dataclass
+class User:
+    name: str
+    age: int
+    email: Optional[str] = None
+
+def is_adult(user: User) -> bool:
+    return user.age >= 18
+
+def format_user_info(user: User) -> str:
+    email_str = user.email if user.email else "no email"
+    return f"{user.name} ({user.age}): {email_str}"
+
+def process_user(user: User) -> Optional[str]:
+    if not is_adult(user):
+        return None
+    return format_user_info(user)
+
+
+# Testing old version
+print(process_user_data(("Alice", 25, "alice@example.com")))
+print(process_user_data(("Bob", 16)))
+
+# Testing new version
+user1 = User("Alice", 25, "alice@example.com")
+user2 = User("Bob", 16)
+
+print(process_user(user1))
+print(process_user(user2))
+
+
+# Another example
+def get_value(key: str, data: dict[str, int]) -> Optional[int]:
+    return data.get(key)
+
+sample_data = {"a": 1, "b": 2}
+result = get_value("a", sample_data)
+if result is not None:
+    print(f"Found: {result}")

prep-exercises/why_we_use_types.py

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+def half(value):
+    return value / 2 
+
+def double(value):
+    return value * 2 
+
+def second(value):
+    return value[1]
+
+# Prediction: double("22") will return "2222" because * operator repeats strings
+print(double("22"))
+
+# Testing other cases
+print(half(22))
+# print(half("hello"))  # This will error
+# print(half("22"))  # This will error
+
+print(double(22))
+print(double("hello"))
+
+# print(second(22))  # This will error
+print(second("hello"))
+print(second("22"))
+
+def double_bug(number):
+    return number * 2
+
+print(double_bug(10))  # Returns 20 (correctly doubles the number)