London | 26-ITP-July | Raihan Sharif | Sprint 5 | Prep Exercises

sprint-5-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
+
+
+
+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 is_developer(person: Person) -> bool:
+    return person.is_developer
+
+print(is_developer(imran))
+
+# As expected, there is an error because the is_developer attribute is not present in the Person class.

sprint-5-exercises/advantage_of_using_methods.txt

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+Encapsulation: 
+Data and methods are packaged together to form one cohesive unit.
+This allows great control of access and modification of the data,
+presenting an interface to the user, and hiding the implementation details.
+
+The class/object can impose rules on access and modification. E.g. balance can't
+be negative.
+
+Implementation can also be changed without breaking the interface which 
+should be reliable and consistent over time.
+
+Ease of use:
+Makes it easier for users of the data, as they only need to reason about
+the interface, not the implementation details. E.g. methods that operate on an object
+can be easily with the dot notation and IDE autocomplete.
+

sprint-5-exercises/bank_account_annotations.py

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+from typing import Dict
+
+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,
+}
+
+# the amount is int pence not float pounds
+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-exercises/dataclass_person.py

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+# convert person class to a dataclass
+import datetime as dt
+from dataclasses import dataclass
+
+@dataclass
+class Person:
+    name: str
+    birthdate: dt.date
+    preferred_operating_system: str
+
+    def is_adult(self) -> bool:
+        today = dt.date.today()
+        years = today.year - self.birthdate.year
+        # python does a lexicographical comparison of the elements in the tuples
+        # only checks the days if the months are equal
+
+        had_birthday_this_year = (today.month, today.day) >= (self.birthdate.month, self.birthdate.day)
+        age = years if had_birthday_this_year else years - 1
+        return age >= 18
+
+        # note: the above is necessary because with my old version, if the original birthday is on feb 29
+        # then it would try to create a new date of feb 29 on a non-leap year and crash
+
+imran = Person("Imran", dt.date(2009,8,6), "Ubuntu")
+print(imran.is_adult())

sprint-5-exercises/fix_double.py

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+def double(number):
+    # return number * 3
+    return number * 2. # the fix
+
+print(double(10))
+
+# bug: function is called double, but returns tripple of what is given as input.

sprint-5-exercises/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=12)
+aisha = Person(name="Aisha", children=[], age=15)
+
+imran = Person(name="Imran", children=[fatma, aisha], age=40)
+
+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-exercises/inheritance_check.py

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+
+# parent class has two string fields, first_name, last_name
+# a method that return a string which joins the two names with a space
+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}"
+
+
+# extends parent class
+# add ability to change last name, store previous last names in a list
+# a method that prints first and last name as well as the original last name of Child
+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")
+print(person1.get_name()) # inherit from Parent class, output = "Elizaveta Alekseeva"
+print(person1.get_full_name()) # method of Child class, output = "Elizaveta Alekseeva" no previous surname
+person1.change_last_name("Tyurina") # changes last name of person1, adds "Alekseeva" to previous names list
+print(person1.get_name()) # last name has changed, output = "Elizaveta Tyurina"
+print(person1.get_full_name()) # includes maiden name, output = "Elizaveta Tyurina (née Alekseeva)"
+
+person2 = Parent("Elizaveta", "Alekseeva")
+print(person2.get_name()) # output = "Elizaveta Alekseeva"
+print(person2.get_full_name()) # AttrbuteError - the Parent class does not have get_full_name() method
+person2.change_last_name("Tyurina") # same again
+print(person2.get_name()) # no problems, same as line 40
+print(person2.get_full_name()) # again, no get_full_name() method in this Parent class. Same as line 41

sprint-5-exercises/laptop_enums.py

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+from dataclasses import dataclass
+from enum import Enum
+from typing import List
+from collections import Counter
+
+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
+
+
+def find_possible_laptops(laptops: List[Laptop], person: Person) -> List[Laptop]:
+    possible_laptops = []
+    for laptop in laptops:
+        if laptop.operating_system == person.preferred_operating_system:
+            possible_laptops.append(laptop)
+    return possible_laptops
+
+
+laptops = [
+    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),
+]
+
+
+# take input (name, age, preferred os), create Person object
+# show them how many laptops with their chosen OS are available
+# if there is a different os with more laptops, tell user they are more likely to get a laptop
+# if they choose that os
+
+# loops forever until alphabetic string provided
+def person_name_input() -> str:
+    name = input("Enter your first name: ")
+    while True:
+        if (name.isalpha()):
+            return name
+        name = input("invalid first name, please enter only letters: ")
+
+# loops forever until numeric input is provided
+def person_age_input() -> int:
+    age = input("Enter your age: ")
+    while True:
+        if (age.isnumeric()):
+            return int(age)
+        age = input("Invalid age, please enter only integer value: ")
+
+# loops forever until a valid OS is chosen
+def preferred_os_input() -> OperatingSystem:
+    os_options = [member.name for member in OperatingSystem]
+    os_choice = input(f"Enter your preferred laptop from {os_options}: ").strip().upper()
+
+    while True:
+        if (os_choice in os_options):
+            return OperatingSystem[os_choice]
+        os_choice = input(f"Invalid choice, check spelling and spaces. choices:  {os_options}: ").strip().upper()
+
+
+print(f"Welcome to the CYF library. Enter your details to begin")
+
+name = person_name_input()
+age = person_age_input()
+preferred_os = preferred_os_input()
+
+person: Person = Person(name, age, preferred_os)
+
+possible_laptops = find_possible_laptops(laptops, person)
+
+print(f"There are {len(possible_laptops)} laptops with your preferred OS.")
+
+# keep only non-preferred OS, and then see if there there is an OS with more laptops available
+non_preferred_os = filter(lambda x: x.operating_system != person.preferred_operating_system, laptops)
+
+counter = Counter(laptop.operating_system for laptop in non_preferred_os)
+most_common_os, count = counter.most_common(1)[0]
+
+if (count > len(possible_laptops)):
+    print(f"there are {count} latops with {most_common_os.name} operating system. You are more likely to get a laptop if you choose {most_common_os.name} ")

sprint-5-exercises/person_class_errors.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)
+
+# Understand the errors from running mypy on this code
+
+# Person_class_errors.py:9: error: "Person" has no attribute "address"  [attr-defined]
+# Because there is type definiton in the constructor of the Person class, mypy checks whether
+# the imran object has an address attribute, and finds that it does not.
+
+# Person_class_errors.py:13: error: "Person" has no attribute "address"  [attr-defined]
+# Same with eliza. It is a Person type object, without an address property, code attempts to
+# print in line 13.

sprint-5-exercises/person_datetime.py

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+# modify to use datetime.date to take in a date of birth
+# store in a field instead of age
+import datetime as dt
+
+class Person:
+    def __init__(self, name: str, birthdate: dt.date, preferred_operating_system: str):
+        self.name = name
+        self.birthdate = birthdate
+        self.preferred_operating_system = preferred_operating_system
+        self.birthdate = birthdate
+
+    def is_adult(self) -> bool:
+        today = dt.date.today()
+        years = today.year - self.birthdate.year
+        # python does a lexicographical comparison of the elements in the tuples
+        # only checks the days if the months are equal
+
+        had_birthday_this_year = (today.month, today.day) >= (self.birthdate.month, self.birthdate.day)
+        age = years if had_birthday_this_year else years - 1
+        return age >= 18
+
+        # note: the above is necessary because with my old version, if the original birthday is on feb 29
+        # then it would try to create a new date of feb 29 on a non-leap year and crash
+
+imran = Person("Imran", dt.date(2008,8,6), "Ubuntu")
+print(imran.is_adult())

sprint-5-exercises/predict_double.py

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+def half(value):
+    return value / 2 
+
+def double(value):
+    return value * 2 
+
+def second(value):
+    return value[1]
+
+
+# predict what double("22") will do
+
+print(double("22"))
+
+# I predict that the function will return "2222", as the * operator is overloaded in python. 
+# So that if a number is given, it performs the arithmetic operation, but if a string is given it just repeats
+# the string 2 times

sprint-5-exercises/type_guided_refactoring.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 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", "macOs"]),
+]
+
+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}")