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/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/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}")