Move python-self-type to root and rename for consistency (#399)

Author: gahjelle

python-shebang/python-self-type/README.md python-self-type/README.mdpython-shebang/python-self-type/README.md renamed to python-self-type/README.md

@@ -0,0 +1,66 @@
+import random
+from dataclasses import dataclass
+
+
+@dataclass
+class BankAccount:
+    account_number: int
+    balance: float
+
+    def display_balance(self) -> "BankAccount":
+        print(f"Account Number: {self.account_number}")
+        print(f"Balance: ${self.balance:,.2f}\n")
+        return self
+
+    def deposit(self, amount: float) -> "BankAccount":
+        self.balance += amount
+        return self
+
+    def withdraw(self, amount: float) -> "BankAccount":
+        if self.balance >= amount:
+            self.balance -= amount
+        else:
+            print("Insufficient balance")
+        return self
+
+
+@dataclass
+class SavingsAccount(BankAccount):
+    interest_rate: float
+
+    @classmethod
+    def from_application(
+        cls, deposit: float = 0, interest_rate: float = 1
+    ) -> "SavingsAccount":
+        # Generate a random seven-digit bank account number
+        account_number = random.randint(1000000, 9999999)
+        return cls(account_number, deposit, interest_rate)
+
+    def calculate_interest(self) -> float:
+        return self.balance * self.interest_rate / 100
+
+    def add_interest(self) -> "SavingsAccount":
+        self.deposit(self.calculate_interest())
+        return self
+
+
+account = BankAccount(account_number=1534899324, balance=50)
+(
+    account.display_balance()
+    .deposit(50)
+    .display_balance()
+    .withdraw(30)
+    .display_balance()
+)
+
+savings = SavingsAccount.from_application(deposit=100, interest_rate=5)
+(
+    savings.display_balance()
+    .add_interest()
+    .display_balance()
+    .deposit(50)
+    .display_balance()
+    .withdraw(30)
+    .add_interest()
+    .display_balance()
+)