London | 26-Jul-SDC | Alex Jamshidi | Sprint 5 | Prep Exercises

sprint-5-prep-exercises/.gitignore

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+.venv

sprint-5-prep-exercises/exercise_01.py

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+# Exercise
+# Predict what double("22") will do. 
+# It will treat "22" as a integer and return 11 as an integer 
+
+# Then run the code and check. 
+def double(value):
+    return value * 2
+
+print(double("22"))
+
+# Did it do what you expected? Why did it return the value it did?
+# No, it treated it like a string, so instead of trying to do math, it did string repetition.

sprint-5-prep-exercises/exercise_02.py

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+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?
+
+# Potential bug: Code says double and it is multiplying by 3
+
+# It could be fixed by changing the name of the function to triple, or the integer to 2.

sprint-5-prep-exercises/exercise_03.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}")

sprint-5-prep-exercises/exercise_04_and_05.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)
+
+# exercise_4_and_5.py:9: error: "Person" has no attribute "address"  [attr-defined]
+# exercise_4_and_5.py:13: error: "Person" has no attribute "address"  [attr-defined]
+# Found 2 errors in 1 file (checked 1 source file)
+
+# There is no address attribute for a Person, only name, age and preferred operating system.
+
+# Add the is_adult code to the file you saved earlier.
+def is_adult(person: Person) -> bool:
+    return person.age >= 18
+
+print(is_adult(imran))
+
+# 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.
+
+def is_banana(person: Person) -> bool:
+    return person.banana
+
+print(is_banana(imran))
+
+# exercise_4_and_5.py:31: error: "Person" has no attribute "banana"  [attr-defined]

sprint-5-prep-exercises/exercise_06.py

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+# Think of the advantages of using methods instead of free functions. Write them down in your notebook.
+
+# Better readability of code
+# Encapsulation of that function only to class - cleaner and better security.

sprint-5-prep-exercises/exercise_07.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):
+        dob = self.dob
+        today = date.today()
+        if dob.year > today.year - 18: return False
+        if dob.year == today.year - 18:
+            if dob.month > today.month: return False
+            if dob.month == today.month:
+                if dob.day > today.day: return False
+        return True
+
+
+imran = Person("Imran", date(2004, 8, 31), "Ubuntu")
+print(imran.is_adult())
+
+# 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.

sprint-5-prep-exercises/exercise_08.py

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+# Write a Person class using @datatype which uses a datetime.date for date of birth, rather than an int for age.
+from dataclasses import dataclass
+from datetime import date
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    dob: date
+    preferred_operating_system: str
+
+# Re-add the is_adult method to it.
+    def is_adult(self):
+        dob = self.dob
+        today = date.today()
+        if dob.year > today.year - 18: return False
+        if dob.year == today.year - 18:
+            if dob.month > today.month: return False
+            if dob.month == today.month:
+                if dob.day > today.day: return False
+        return True
+
+
+imran = Person("Imran", date(2004, 8, 31), "Ubuntu")
+print(imran.is_adult())

sprint-5-prep-exercises/exercise_09.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=82)
+aisha = Person(name="Aisha", children=[], age=83)
+
+imran = Person(name="Imran", children=[fatma, aisha], age=102)
+
+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-5-prep-exercises/exercise_10.py

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+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 == person.preferred_operating_systems:
+            possible_laptops.append(laptop)
+    return possible_laptops
+
+
+people = [
+    Person(name="Imran", age=22, preferred_operating_systems=["Ubuntu"]),
+    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}")
+
+# Try changing the type annotation of Person.preferred_operating_system from str to List[str].
+# Run mypy on the code.
+
+# exercise_10.py:29: error: Argument "preferred_operating_system" to "Person" has incompatible type "str"; expected "list[str]"  [arg-type]
+# exercise_10.py:30: error: Argument "preferred_operating_system" to "Person" has incompatible type "str"; expected "list[str]"  [arg-type]
+
+
+# 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.
+
+# exercise_10.py:23: error: "Person" has no attribute "preferred_operating_system"; maybe "preferred_operating_systems"?  [attr-defined]
+# exercise_10.py:29: error: Unexpected keyword argument "preferred_operating_system" for "Person"; did you mean "preferred_operating_systems"?  [call-arg]
+# exercise_10.py:30: error: Unexpected keyword argument "preferred_operating_system" for "Person"; did you mean "preferred_operating_systems"?  [call-arg]
+
+# Fix all of the places that mypy tells you need changing. Make sure the program works as you’d expect.

sprint-5-prep-exercises/exercise_11.py

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+# 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.
+
+# ----- Imports
+from dataclasses import dataclass
+from enum import Enum
+import sys
+
+ # ----- Classes and Enums
+class OperatingSystem(Enum):
+    MACOS = "macOS"
+    ARCH = "Arch Linux"
+    UBUNTU = "Ubuntu"
+    WINDOWS = "Windows"
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    age: int
+    preferred_operating_system: OperatingSystem
+
+@dataclass(frozen=True)
+class Laptop:
+    id: int
+    operating_system: OperatingSystem
+
+ # ----- Functions
+def count_laptops(laptops: list[Laptop], laptop_counts: dict[str, int]):
+    for laptop in laptops:
+        laptop_counts[laptop.operating_system] += 1 
+
+def check_laptop_abundance(user: Person, laptop_counts: dict[OperatingSystem, int]):
+    abundant_laptops = []
+    for laptop in laptop_counts:
+        if laptop_counts[laptop] > laptop_counts[user.preferred_operating_system]:
+            abundant_laptops.append(laptop.value)
+    if len(abundant_laptops) > 0:
+        print("\nIf you are willing to accept another operating system you may get a laptop sooner.")
+        print("We have more laptops available with the following OS:")
+        for laptop in abundant_laptops:
+            print(laptop)
+
+ # ----- Data and Constants
+laptops = [
+    Laptop(id=1, operating_system=OperatingSystem.ARCH),
+    Laptop(id=2, operating_system=OperatingSystem.ARCH),
+    Laptop(id=3, operating_system=OperatingSystem.UBUNTU),
+    Laptop(id=4, operating_system=OperatingSystem.UBUNTU),
+    Laptop(id=5, operating_system=OperatingSystem.UBUNTU),
+    Laptop(id=6, operating_system=OperatingSystem.UBUNTU),
+    Laptop(id=7, operating_system=OperatingSystem.MACOS),
+    Laptop(id=8, operating_system=OperatingSystem.MACOS),
+]
+laptop_counts = {
+    OperatingSystem.MACOS: 0,
+    OperatingSystem.ARCH: 0,
+    OperatingSystem.UBUNTU: 0,
+    OperatingSystem.WINDOWS: 0
+}
+
+ # ----- Script
+user_name = input("Please enter your full name:\n")
+user_age_str = input("Please enter your age:\n")
+
+try:
+    user_age = int(user_age_str)
+except ValueError:
+    sys.exit("Error: Age should be a number.")
+
+user_operating_system_str = input("Please enter your preferred operating system (options: ARCH, UBUNTU, MACOS, WINDOWS):\n")
+
+if user_operating_system_str not in OperatingSystem.__members__:
+    sys.exit("Error: Operating system should be written in all caps from given options.")
+else: user_operating_system = OperatingSystem[user_operating_system_str]
+
+user = Person(user_name, user_age, user_operating_system)
+
+count_laptops(laptops, laptop_counts)
+print(f"\nThe number of available laptops with {user_operating_system.value} is: {laptop_counts[user_operating_system]}")
+
+check_laptop_abundance(user, laptop_counts)