Manchester | 26-SDC-Jul | Fithi Teklom | Sprint 5 | Prep exercises

sprint5-prep-exercises/add_is_adult.py

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+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
+
+
+def is_adult(person: Person) -> bool:
+    return person.age >= 18
+
+
+def get_address(person: Person) -> str:
+    return person.address
+
+
+imran = Person("Imran", 22, "Ubuntu")
+
+print(imran.name)
+print(is_adult(imran))

sprint5-prep-exercises/advantagesOfMethods.py

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+# Better organisation — behaviour related to a class stays together with that class.
+
+# Easier to discover — if I have a Person, I can look at the Person class to see what it can do.
+
+# More readable — person.is_adult() clearly shows that is_adult is behaviour associated with a Person.
+
+# Encapsulation — other code doesn't need to know the internal details of how Person calculates something.
+
+# Easier maintenance/refactoring — if the internal representation changes, such as changing age to date_of_birth, we can update the method while callers can continue using person.is_adult().

sprint5-prep-exercises/classesAndoObjects.py

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+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)
+
+#The error is that the code tries to access an attribute called address, but the Person class does not define an address attribute. 
+#Mypy knows that imran and eliza are Person objects, so it can detect that .address does not exist before we run the program.

sprint5-prep-exercises/data_class.py

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+from datetime import date
+from dataclasses import dataclass
+
+
+@dataclass
+class Person:
+    name: str
+    date_of_birth: date
+    preferred_operating_system: str
+
+    def is_adult(self):
+        today = date.today()
+        age = today.year - self.date_of_birth.year
+
+        return age >= 18
+
+
+imran = Person("Imran", date(2000, 10, 10), "Ubuntu")
+print(imran.is_adult())

sprint5-prep-exercises/enums.py

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+from dataclasses import dataclass
+from enum import Enum
+import sys
+
+
+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
+
+
+# 1. The library already has some laptops
+laptops = [
+    Laptop(1, "Dell", "XPS", 13, OperatingSystem.ARCH),
+    Laptop(2, "Dell", "XPS", 15, OperatingSystem.UBUNTU),
+    Laptop(3, "Dell", "XPS", 15, OperatingSystem.UBUNTU),
+    Laptop(4, "Apple", "MacBook", 13, OperatingSystem.MACOS),
+]
+
+
+# 2. Get the person's name
+name = input("Enter your name: ")
+
+
+# Get age as text, then convert it to int immediately
+age_input = input("Enter your age: ")
+
+try:
+    age = int(age_input)
+except ValueError:
+    print("Error: age must be a whole number.", file=sys.stderr)
+    sys.exit(1)
+
+
+# Get operating system as text, then convert it to an enum immediately
+os_input = input(
+    "Enter your preferred operating system "
+    "(Ubuntu, Arch Linux, macOS): "
+)
+
+try:
+    preferred_os = OperatingSystem(os_input)
+except ValueError:
+    print(
+        "Error: operating system must be Ubuntu, Arch Linux, or macOS.",
+        file=sys.stderr,
+    )
+    sys.exit(1)
+
+
+# Now we have correctly typed data, so create the Person
+person = Person(
+    name=name,
+    age=age,
+    preferred_operating_system=preferred_os,
+)
+
+
+# 3. Count laptops with the person's preferred operating system
+preferred_count = 0
+
+for laptop in laptops:
+    if laptop.operating_system == person.preferred_operating_system:
+        preferred_count += 1
+
+
+print(
+    f"The library has {preferred_count} laptop(s) "
+    f"with {person.preferred_operating_system.value}."
+)
+
+
+# 4. Check whether another operating system has more laptops
+for operating_system in OperatingSystem:
+
+    # Don't compare their preferred OS with itself
+    if operating_system == person.preferred_operating_system:
+        continue
+
+    count = 0
+
+    for laptop in laptops:
+        if laptop.operating_system == operating_system:
+            count += 1
+
+    if count > preferred_count:
+        print(
+            f"If you are willing to use {operating_system.value}, "
+            f"you are more likely to get a laptop because "
+            f"the library has {count} available."
+        )
+
+

sprint5-prep-exercises/generic.py

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+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    age: int
+    children: list
+
+
+fatma = Person(name="Fatma", age= 26, children=[])
+aisha = Person(name="Aisha", age = 20, children=[])
+
+imran = Person(name="Imran", age = 45, 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)

sprint5-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 = []
+
+    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" (previously {self.previous_last_names[0]})"
+
+        return f"{self.first_name} {self.last_name}{suffix}"
+
+
+person1 = Child("Sara", "Ali")
+
+print(person1.get_name())
+print(person1.get_full_name())
+
+person1.change_last_name("Ahmed")
+
+print(person1.get_name())
+print(person1.get_full_name())
+
+
+person2 = Parent("Sara", "Ali")
+
+print(person2.get_name())
+
+# These lines would cause errors because these methods
+# only exist in Child, not Parent:
+
+# print(person2.get_full_name())
+# person2.change_last_name("Ahmed")
+
+print(person2.get_name())
+
+# This would also cause an error:
+# print(person2.get_full_name())
+
+
+# The important inheritance relationship is:
+
+# Parent
+#   │
+#   ├── get_name()
+#   │
+#   ▼
+# Child
+#   ├── inherits get_name()
+#   ├── adds change_last_name()
+#   └── adds get_full_name()
+
+# So a Child can use the inherited Parent method, but a Parent cannot use methods that only exist in Child.

sprint5-prep-exercises/limits_of_type_checking.py

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+# Read the above code and write down what the bug is. How would you fix it?
+
+def double(number):
+    # return number * 3
+    return number * 2  # I would fix it like this 
+
+print(double(10))
+
+#Because double function is expected to double or multiply a number by two but in contrast it is multiplying by 3.

sprint5-prep-exercises/methods.py

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+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):
+        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 >= 18
+
+
+imran = Person("Imran", date(2000, 2, 10), "Ubuntu")
+print(imran.is_adult())

sprint5-prep-exercises/predict_double.py

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+# 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?
+def half(value):
+    return value / 2 
+
+def double(value):
+    return value * 2 
+
+def second(value):
+    return value[1]
+
+print(double(22))
+
+#So I predicted the string would be doubled(repeated) --> "2222"
+#As in Python, multiplying a string by an integer means repeat the string

sprint5-prep-exercises/type_annotation.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 = {
+    "Sima": 700,
+    "Linn": 545,
+    "Georg": 831,
+}
+
+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}")
+
+