London | 26-SDC-March | Zobeir Rigi | Sprint 5 | prep-exercises

sprint-five-prep/classes_objects.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)
+
+def is_adult(person: Person) -> bool:
+    return person.age >= 18
+
+print(is_adult(imran))
+
+def get_id(person: Person) -> int:
+    return person.id
+# Exercise
+# Save the above code to a file, and run it through mypy.
+# Read the error, and make sure you understand what it’s telling you.
+# Answer : "Person" has no attribute "address". both instances of "Person", and they dont have address att.
+
+# Exercise
+# Add the is_adult code to the file you saved earlier.
+# Run it through mypy - notice that no errors are reported - mypy understands that Person has a property named age so is happy with the function.
+# Write a new function in the file that accepts a Person as a parameter and
+#  tries to access a property that doesn’t exist.
+#  Run it through mypy and check that it does report an error.
+
+# Answer : "Person" has no attribute "id". 

sprint-five-prep/dataclass.py

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+# ✍️exercise
+# Write a Person class using @datatype which uses a datetime.date for date of birth, rather than an int for age.
+
+# Re-add the is_adult method to it.
+
+from dataclasses import dataclass
+from datetime import date
+
+@dataclass(frozen=True)
+class Person:
+    name:str
+    date_of_birth: date
+    prefered_o_s: str
+
+    def is_adult(self)->bool:
+        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
+
+
+imran1 = Person("Imran", date(2002, 5, 10), "Ubuntu")
+imran2 = Person("Imran", date(2002, 5, 10), "Ubuntu")
+
+print(imran1 == imran2)  
+
+print(imran1.is_adult())
+

sprint-five-prep/enums.py

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+from dataclasses import dataclass
+from enum import Enum
+from typing import List
+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
+
+
+laptops: List[Laptop] = [
+    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),
+]
+
+
+def parse_os(user_input: str) -> OperatingSystem:
+    for os in OperatingSystem:
+        if os.value.lower() == user_input.lower():
+            return os
+    raise ValueError("Invalid operating system")
+
+
+def count_laptops(os: OperatingSystem) -> int:
+    return sum(1 for laptop in laptops if laptop.operating_system == os)
+
+
+
+def most_available_os() -> OperatingSystem:
+    return max(OperatingSystem, key=lambda os: count_laptops(os))
+
+
+
+# Main program
+try:
+    name = input("Enter your name: ").strip()
+
+    age_input = input("Enter your age: ").strip()
+    age = int(age_input)
+    if age < 0:
+        raise ValueError("Age must be a positive number")
+
+    os_input = input("Enter OS (macOS, Arch Linux, Ubuntu): ").strip()
+    preferred_os = parse_os(os_input)
+
+except ValueError as e:
+    print(f"Error: {e}", file=sys.stderr)
+    sys.exit(1)
+
+
+person = Person(name, age, preferred_os)
+
+available = count_laptops(person.preferred_operating_system)
+print(f"\nWe have {available} laptops with {person.preferred_operating_system.value}.")
+
+best = most_available_os()
+if best != person.preferred_operating_system:
+    more = count_laptops(best)
+    print(f"If you're flexible, {best.value} has more laptops available ({more}).")
+
+
+
+# ✍️exercise
+# Write a program which:
+
+# Already has a list of Laptops that a library has to lend out.
+# Accepts user input to create a new Person - it should use the input 
+# function to read a person’s name, age, and preferred operating system.
+# Tells the user how many laptops the library has that have that operating system.
+# If there is an operating system that has more laptops available, tells the user 
+# that if they’re willing to accept that operating system they’re more likely to get a laptop.
+# You should convert the age and preferred operating system input from the user into more
+# constrained types as quickly as possible, and should output errors to stderr and terminate 
+# the program with a non-zero exit code if the user input bad values.

sprint-five-prep/first.py

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+# ✍️exercise
+# Predict what double("22") will do. Then run the code and check.
+#  Did it do what you expected? no
+#  Why did it return the value it did? it just concatenated (repeated) the string. I expected it returns 44, but there is type issue.
+
+
+def double(value):
+    return value * 2 
+
+print(double("22"))
+
+# ---------------
+def double(number):
+    return number * 3
+
+print(double(10))
+
+# ✍️exercise
+# Read the above code and write down what the bug is. How would you fix it?
+# it will return 30, but the function name is double, so we have to change the function name to triple or change the return statement to number * 2. 
+

sprint-five-prep/generics.py

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+from dataclasses import dataclass
+from typing import List
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    children: List["Person"]
+    age: int  
+
+fatma = Person(name="Fatma", children=[], age=10)  
+aisha = Person(name="Aisha", children=[], age=8)  
+
+imran = Person(name="Imran", children=[fatma, aisha], age=35)
+
+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)
+
+# Fix the above code so that it works. You must not change the print on line 17 - we do want to print the children’s ages.
+#  (Feel free to invent the ages of Imran’s children.)

sprint-five-prep/inheritance.py

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+# ✍️exercise
+# Play computer with this code. Predict what you expect each line will do. Then run the code and check your predictions.
+#  (If any lines cause errors, you may need to comment them out to check later lines).
+
+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}"
+
+# Child class (inherits from Parent)
+class Child(Parent):
+    def __init__(self, first_name: str, last_name: str):
+        super().__init__(first_name, last_name)    # Call Parent constructor
+        self.previous_last_names: list[str] = []  # New property (only Child has this)
+
+
+    def change_last_name(self, last_name) -> None:
+        self.previous_last_names.append(self.last_name) # Save old last name
+        self.last_name = last_name  # Update to new last name
+
+    def get_full_name(self) -> str:   # Extra method only in Child
+        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()) # Inherited method from Parent 
+# Output: Elizaveta Alekseeva
+
+print(person1.get_full_name()) 
+#  Method from Child , 
+# Output: Elizaveta Alekseeva
+
+
+person1.change_last_name("Tyurina") 
+# Change last name
+
+print(person1.get_name()) 
+# Parent method still works , 
+# Output: Elizaveta Tyurina (née Alekseeva)
+
+print(person1.get_full_name())
+
+
+# Using Parent
+person2 = Parent("Elizaveta", "Alekseeva")
+
+# Works (Parent method), 
+# Output: Elizaveta Alekseeva
+print(person2.get_name())
+
+
+# print(person2.get_full_name()) 
+# ERROR: Parent has no method "get_full_name"
+
+# person2.change_last_name("Tyurina") 
+# ERROR: Parent has no method "change_last_name"
+
+print(person2.get_name())
+# print(person2.get_full_name())
+
+
+
+
+
+
+# Inheritance allows a class (Child) to reuse and extend another class (Parent).
+# When calling a method, Python first checks the subclass, then the superclass.
+# The Child can add or override methods, but the Parent cannot access Child-specific methods.
+
+# Difference between inheritance and composition:
+# - Inheritance: "is-a" (Child IS a Parent)
+# - Composition: "has-a" (Object HAS another object)

sprint-five-prep/methods.py

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+# ✍️exercise
+# Change the Person class to take a date of birth (using the standard library’s datetime.date class) and store it in a field instead of age.
+# Update the is_adult method to act the same as before.
+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
+
+        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, 10), "Ubuntu")
+eliza = Person("Eliza", date(1990, 8, 3), "Arch Linux")
+
+print(imran.is_adult())
+print(eliza.is_adult())
+
+
+
+
+
+
+
+
+
+# ✍️exercise
+# Think of the advantages of using methods instead of free functions.
+#  Write them down in your notebook.
+# Encapsulation 
+# The class controls its own logic
+# Example: You change from age → date_of_birth
+# Only the class needs to change,  External code still works:person.is_adult()
+# Methods = behavior belongs to the object

sprint-five-prep/type_checking_mypy.py

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+# ✍️exercise
+# Do not run the following code.
+# This code contains bugs related to types. They are bugs mypy can catch.
+# Read this code to understand what it’s trying to do.
+#  Add type annotations to the method parameters and return types of this code.
+#  Run the code through mypy,and fix all of the bugs that show up. When you’re confident all of the type annotations
+# are correct, and the bugs are fixed, run the code and check it works.
+
+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, name="Tobi", amount=913)
+open_account(balances, name="Olya", amount=713)
+
+total_pence = sum_balances(balances)
+total_string = format_pence_as_string(total_pence)
+
+print(f"The bank accounts total {total_string}")