London | 26-SDC-Mar | Ebrahim Beiati-Asl | Sprint 5 |Sprint 5 prep

sprint-5/Type-checking-with-mypy.py

@@ -0,0 +1,40 @@
+#==============================================================================
+# 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: dict[str, int] = {
+    "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}")

sprint-5/Type-guided-refactorings.py

@@ -0,0 +1,55 @@
+#exercise
+# Try changing the type annotation of Person.preferred_operating_system from str to List[str].
+
+# Run mypy on the code.
+
+# It tells us different places that our code is now wrong, because we’re passing values of the wrong type.
+
+# We probably also want to rename our field - lists are plural. Rename the field to preferred_operating_systems.
+
+# Run mypy again.
+
+# Fix all of the places that mypy tells you need changing. Make sure the program works as you’d expect.
+
+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: List[Laptop] = []
+    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}")

sprint-5/classes_and_objects.py

@@ -0,0 +1,32 @@
+# Exercise 1 — 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.
+
+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) # mypy error: "Person" has no attribute "address"
+
+eliza = Person("Eliza", 34, "Arch Linux")
+print(eliza.name)
+print(eliza.address) # mypy error: "Person" has no attribute "address"
+
+# Exercise 2 — 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.
+def is_adult(person: Person) -> bool:
+    return person.age >= 18
+
+print(is_adult(imran)) # True
+
+def get_favorite_food(person: Person) -> str:
+    return person.favorite_food # mypy error: "Person" has no attribute "favorite_food"
+

sprint-5/dataclasses_exercise.py

@@ -0,0 +1,25 @@
+from dataclasses import dataclass
+from datetime import date
+# 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.
+
+
+@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
+
+        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, 1, 1), "Ubuntu")
+imran2 = Person("Imran", date(2000, 1, 1), "Ubuntu")
+print(imran.is_adult())
+print(imran == imran2) # True, because dataclasses automatically generate an __eq__ method that compares the fields of the dataclass.

sprint-5/enums_exercise.py

@@ -0,0 +1,65 @@
+# 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.
+
+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 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 convert_os(user_input: str) -> OperatingSystem:
+    for os_value in OperatingSystem:
+        if user_input.lower() == os_value.value.lower():
+            return os_value
+        print(f"Error: '{user_input}' is not a valid operating system.", file=sys.stderr)
+        sys.exit(1)
+
+# Get user input
+name = input("Enter your name: ").strip()
+age_input = input("Enter your age: ").strip()
+if not age_input.isdigit():
+    print(f"Error: '{age_input}' age must be a number.", file=sys.stderr)
+    sys.exit(1)
+age = int(age_input)
+
+os_input = input("Enter your preferred operating system (macOS, Arch Linux, Ubuntu): ").strip()
+preferred_os = convert_os(os_input)
+
+# Count laptops with the preferred operating system
+matching_laptops = [laptop for laptop in laptops if laptop.operating_system == preferred_os]
+print(f"\nHi {name}, there are {len(matching_laptops)} laptops available with {preferred_os.value}.")
+
+# Check if there are better laptops with a different operating system
+counts ={os: 0 for os in OperatingSystem}
+for laptop in laptops:
+    counts[laptop.operating_system] += 1
+
+best_os = max(counts, key=counts.get)
+if best_os != preferred_os:
+    print(f"if you’re willing to accept {best_os.value} you’re more likely to get a laptop, as there are {counts[best_os]} available.")

sprint-5/generics_exercise.py

@@ -0,0 +1,24 @@
+#exercise
+# 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.)
+from dataclasses import dataclass
+from typing import List
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    age: int
+    children: List["Person"]
+
+fatma = Person(name="Fatma", age=10, children=[])
+aisha = Person(name="Aisha", age=5, children=[])
+
+imran = Person(name="Imran", age=40, 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)

sprint-5/inheritance.py

@@ -0,0 +1,54 @@
+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")
+#first name is Elizaveta, last name is Alekseeva, no previous last names
+print(person1.get_name())
+#Elizaveta Alekseeva
+
+print(person1.get_full_name())
+#Elizaveta Alekseeva
+
+person1.change_last_name("Tyurina")
+#previous last name is now Alekseeva, current last name is Tyurina
+
+print(person1.get_name())
+#Elizaveta Tyurina
+
+print(person1.get_full_name())
+#Elizaveta Tyurina (née Alekseeva)
+
+person2 = Parent("Elizaveta", "Alekseeva")
+# first name is Elizaveta, last name is Alekseeva
+print(person2.get_name())
+#Elizaveta Alekseeva
+
+print(person2.get_full_name())
+# AttributeError: 'Parent' object has no attribute 'get_full_name'
+person2.change_last_name("Tyurina")
+# AttributeError: 'Parent' object has no attribute 'change_last_name'
+print(person2.get_name())
+#Elizaveta Alekseeva, because the last name was not changed
+print(person2.get_full_name())
+# AttributeError: 'Parent' object has no attribute 'get_full_name'

sprint-5/methods.py

@@ -0,0 +1,36 @@
+from datetime import date
+# Exercise 1:
+# Advantages of methods over free functions:
+# 1- Methods keep related data and behavior together
+
+# 2- Methods make code easier to read (person.is_adult() is clearer than is_adult(person))
+
+# 3- Methods reduce the number of parameters (because self already contains the data)
+
+# 4- Methods help mypy catch more errors (because they belong to a specific class)
+
+# 5- Methods make the code more object‑oriented and easier to extend
+
+
+#Exercise 2 — Change Person to use date of birth
+
+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
+
+        has_had_birthday_this_year = (
+            (today.month, today.day) >= (self.date_of_birth.month, self.date_of_birth.day)
+        )
+        if not has_had_birthday_this_year:
+            age -= 1
+        return age >= 18
+
+imran = Person("Imran", date(2000, 1, 1), "Ubuntu")
+print(imran.is_adult())

sprint-5/why_we_use_types.py

@@ -0,0 +1,52 @@
+#=================================================================================
+# Exercise 1: 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 double(value):
+    return value * 2
+
+# Prediction:
+# double("22") will return "2222" because when you multiply a string by
+#  an integer in Python, it concatenates the string that many times.
+#  So "22" * 2 will result in "22" + "22", which is "2222".
+
+print("Exercise 1: double('22') =", double("22"))
+
+# Actual output: double('22') = 2222
+
+#=================================================================================
+# Identify the bug in double()
+#=================================================================================
+def double_bug(number):
+    # Bug: This function is called "double" but multiplies the input by 3 instead of 2.
+    # This is a logic error, not a type error
+    return number * 3
+
+print("Exercise 2:", double_bug(10))
+
+#=================================================================================
+# About half(), double(), second()
+#=================================================================================
+def half(value):
+    return value / 2 
+
+def double(value):
+    return value * 2 
+
+def second(value):
+    return value[1]
+# Prediction and explanation:
+
+# half(22) --> 11.0
+# half("hello") --> TypeError, because you cannot divide a string by a number.
+# half("22") --> TypeError, because you cannot divide a string by a number.
+
+# double_correct(22) --> 44
+# double_correct("hello") --> "hellohello", because multiplying a string by an integer concatenates it.
+# double_correct("22") --> "2222"
+
+# second(22) --> TypeError, because you cannot index an integer.
+# second(0 x 16) --> TypeError, because you cannot index an integer.
+# second("hello") --> "e", because it returns the second character of the string.
+# second("22") --> "2", because it returns the second character of the string.
+