SDC Types Rework

sprint-5-stretch/README.md

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+# Sprint 5 Stretch - Radio Control App
+
+This is part of an app that can be used to control an online radio station
+
+Your task is to:
+1. Upgrade everything use dataclasses
+1. Observe how the given `__str__` method works, and add one to the other classes
+1. When the `__str__` method is called, have it print the duration in formatted mm:ss rather than just seconds
+1. Add a new class of `Person` - you can use your imagination what this includes, but it should have at least a string name
+1. Turn the fields for _artists_, _host_, and _guest_ into `Person` classes
+1. Make a new class `Podcast` that _extends_ the `TalkShow` class, with an extra string field for _sponsor_
+1. Finish implementing the class `Playlist`, and set it to takes a generic, e.g. either `Song` or `TalkShow` or `Podcast`
+
+As you implement, make sure to keep checking with mypy and add your own code at the end to test it works correctly

sprint-5-stretch/requirements.txt

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+mypy

sprint-5-stretch/stretch-radio.py

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+class Song:
+	def __init__(self, artist, duration, title):
+		self.artist = artist # should be a string
+		self.duration = duration # should be an integer in seconds
+		self.title = title # should be a string
+
+	def __str__(self):
+		return f"{self.artist} - {self.title} ({self.duration})"
+
+class TalkShow:
+	def __init__(self, host, guests, duration, title):
+		self.host = host # should be a string
+		self.guests = guests # should be a list of strings
+		self.duration = duration # should be an integer in seconds
+		self.title = title # should be a string
+
+class Playlist:
+	def __init__(self, items):
+		self.items = items # A list of Song or TalkShow
+		self.currently_playing_index = 0
+
+	def play_next(self):
+		pass
+		# TODO: increment the currently_playing_index, when you get to the end loop back to 0
+
+	def get_currently_playing(self):
+		return "todo"
+		# TODO: return a string representation of whatever is playing at the current index
+		# See the __str__ method in Song for an example of how to make a string representation of a class
+
+	def get_total_duration(self):
+		return 0
+		# TODO: return
+
+song_a = Song("Rick Astley", 210, "Never Gonna Give You Up")
+print(song_a)
+
+song_b = Song("Psy", 219, "Gangnam Style")
+funny_songs = Playlist([song_a, song_b])
+print(funny_songs.get_currently_playing())
+
+show_a = TalkShow("Melvyn Bragg", ["Jim Al-Khalili", "Sheila Rowan", "Carolin Crawford"], 2700, "Gravitational Waves")
+

sprint-5/01-predict.py

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+def half(value):
+    return value / 2
+
+def double(value):
+    return value * 2
+
+def second(value):
+    return value[1]
+
+# TASK 1:
+# 1. Predict what you think will happen with each of the following functions
+# 2. Then, test it, and explain in your own words what is actually happening and why
+# (feel free to comment out lines if you think they cause errors or crashes while testing)
+
+print(half(22))
+# Prediction:
+# What actually happens and why:
+
+print(half("22"))
+# Prediction:
+# What actually happens and why:
+
+print(double(22))
+# Prediction:
+# What actually happens and why:
+
+print(double("22"))
+# Prediction:
+# What actually happens and why:
+
+print(second(22))
+# Prediction:
+# What actually happens and why:
+
+print(second(0x16))
+# Prediction:
+# What actually happens and why:
+
+print(second("22"))
+# Prediction:
+# What actually happens and why:

sprint-5/02-playcomputer.js

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+import process from "node:process";
+import readline from "node:readline";
+
+const rl = readline.createInterface({
+	input: process.stdin,
+	output: process.stdout,
+});
+
+rl.question("What URL should we fetch?\n> ", async (url) => {
+	const response = await fetch(url);
+	if (!response.ok) {
+		if (response.body.toLowerCase().includes("permission")) {
+			console.error("You didn't have permission to get that URL");
+		} else {
+			console.error(`The request failed - body: ${response.body}`);
+		}
+		process.exit(1);
+	}
+
+	const contents = await response.json();
+
+	console.log(contents);
+
+	rl.close();
+});
+
+// TASK 2
+// Read through this file and predict what it does.
+// Leave a comment on any lines if you spot any errors, offering an explanation of the problem.

sprint-5/03-fix.py

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+def double(number):
+    return number * 3
+
+print(double(10))
+
+# TASK 3:
+# Read the code and see if you can find any bugs.
+# Write down what the bug is, and how would you fix it?
+# Are there multiple ways you could fix it?

sprint-5/04-addmypy.py

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+def open_account(balances, name, amount):
+    balances[name] = amount
+
+def sum_balances(accounts):
+    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):
+    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("Tobi", 9.13)
+open_account("Olya", "£7.13")
+
+total_pence = sum_balances(balances)
+total_string = format_pence_as_str(total_pence)
+
+print(f"The bank accounts total {total_string}")
+
+# TASK 4
+# 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.

sprint-5/05-predict.py

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+imran = {
+  "name": "Imran",
+  "age": 22,
+  "preferred_operating_system": "Ubuntu",
+}
+
+eliza = {
+  "name": "Eliza",
+  "age": 34,
+  "preferred_operating_system": "Arch Linux",
+}
+
+
+print(imran["name"])
+print(imran["address"])
+
+# TASK 5:
+# This code contains some untyped objects.
+# Try checking it with mypy before running the code and predict what you think will happen when you run the code.
+#
+# Prediction:
+#
+# Can you explain what actualy happens?
+#

sprint-5/06-classes.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)
+
+# TASK 6.1:
+# Run mypy and fix any errors.
+
+# TASK 6.2:
+# Create a new function in this file called likes_apple
+# It should take a person as parameter
+# It returns true if the preferred operating system is "macOS" or "iOS"
+# It should return false for any other preferred os
+# Add all the appropriate type annotations and test it has no errors in mypy
+
+# TASK 6.3:
+# Compare objects and classes
+# What are some advantages and disadvantages of each?

sprint-5/07-methods.txt

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+TASK 7:
+Answer the following questions:
+What is the difference between a method and a function?
+Can you give some advantages of methods over functions?
+

sprint-5/08-implement.py

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+class Person:
+    def __init__(self, name: str, age: int, preferred_car_brand: str):
+        self.name = name
+        self.age = age
+        self.preferred_car_brand = preferred_car_brand
+
+def drivers_license_check(person: Person):
+  if person.is_adult() == True:
+    return 'Valid drivers license'
+
+  return 'This person is underage!'
+
+imran = Person("Imran", 22, "Mercedes")
+print(drivers_license_check(imran)) # should return 'Valid drivers license'
+
+# TASK 8:
+#
+# Add an `is_adult` method into the class, and make sure your code gives the expected output.
+#
+# Change the `Person` class to take a date of birth using
+# the standard library's `datetime.date` class
+# https://docs.python.org/3/library/datetime.html#datetime.date))
+# and store the `date of birth` instead of `age`.
+#
+# Try to run your code now and observe how this change breaks your code.
+# What kind of error do you get? Is it helpful in identifying where your next change needs to be?
+#
+# Now update only the `is_adult` method to fix the error and check everything works correctly.

sprint-5/09-encapsulation.py

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+# TASK 9
+#
+# Having done some research on encapsulation, think about the benefits.
+#
+# Think of some examples and in your own words write down some benefits and trade-offs of using encapsulation in classes:
+#
+#
+#
+
+# STRETCH TASK 9.1
+#
+# In the following  class, make the name property private
+# Add a `get_name()` method to allow read-only access.
+
+class Person:
+    def __init__(self, name: str, age: int):
+        self.name = name
+        self.__age = age
+
+    def is_adult(self):
+      return self.__age >= 18
+
+imran = Person("Imran", 22)
+print(imran.name)
+print(imran.age) # fails
+print(imran.__age) # fails
+print(imran.is_adult()) # works and prints True
+
+eliza = Person("Eliza", 12)
+print(eliza.name)
+print(eliza.age) # fails
+print(imran.__age) # fails
+print(eliza.is_adult()) # works and prints False

sprint-5/10-dataclass.py

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+# TASK 10.1:
+# Copy the code you have so far from task 08-implement.py
+# Convert your existing `Person` class from task 8 into a value type using `@datatype`
+# so you can print the class (and see it's type and properties)
+# and compare class instances that are identical.
+# Make sure your `is_adult` method and `drivers_license_check` free function both work as normal.
+
+# TASK 10.2:
+# Make a new method on your Person class - `greet()` which should return `"Hello <person name>!"` when used.
+
+# TASK 10.3:
+# Read the @datatype documentation here: https://docs.python.org/3/library/dataclasses.html
+# Explain what `frozen=True` does to the class?
+# What other options could you play around with and explore? Offer suggestions for any that would be useful here.

sprint-5/11-predict.py

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+from dataclasses import dataclass
+
+@dataclass(frozen=True)
+class Animal:
+    name: str
+    species: str
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    age: int
+
+@dataclass(frozen=True)
+class FamilyTree:
+    parent: Person
+    members: list
+
+pet = Animal(name="Gromit", species="Dog")
+fatma = Person(name="Fatma", age=4)
+aisha = Person(name="Aisha", age=6)
+imran = Person(name="Imran", age=30)
+
+family = FamilyTree(parent=imran, members=[fatma, aisha, pet])
+
+def print_family_tree(family: FamilyTree):
+    print(family.parent.name)
+    for child in family.members:
+        print(f"{child.name} ({child.age} years old)")
+
+print_family_tree(family)
+
+# TASK 11
+# There is a bug in this code. Can you spot it?
+# Run your code through mypy. Does mypy spot it?
+# Offer an explanation for what is happening.