setup and clarifications for lesson 2 exercise 2

Author: hoffm386

Lesson2-Exercise2-Delete/solution/2.2-Resolution.md

@@ -0,0 +1 @@
+

Lesson2-Exercise2-Delete/solution/README.md

@@ -1,24 +1,28 @@
+import uuid
+
 class ExpenseTracker:
     def __init__(self):
         self.expenses = []
-        self.total = 0
-        self._next_id = 1
 
-    def add_expense(self, amount, category):
-        expense_id = self._next_id
+    @property
+    def total(self):
+        return sum([e["amount"] for e in self.expenses])
+
+    # ------------- Create -------------
+    def add_expense(self, amount, category=None):
+        expense_id = str(uuid.uuid4())
         expense = {"id": expense_id, "amount": amount, "category": category}
         self.expenses.append(expense)
-        self.total += amount
-        self._next_id += 1
         return expense_id
 
+    # ------------- Read -------------
+    def list_expenses_by_category(self, category):
+        return [e for e in self.expenses if e.get("category") == category]
+
     def get_expense(self, expense_id):
         return next((e for e in self.expenses if e["id"] == expense_id), None)
 
+    # ------------- Delete -------------
     def delete_expense(self, expense_id):
-        # Locate the expense to ensure it exists before removal
         expense_to_delete = self.get_expense(expense_id)
-        if expense_to_delete:
-            # Subtract the amount from total to maintain integrity
-            self.total -= expense_to_delete["amount"]
-            self.expenses.remove(expense_to_delete)
+        self.expenses.remove(expense_to_delete)

Lesson2-Exercise2-Delete/solution/src/__init__.py

@@ -0,0 +1 @@
+

Lesson2-Exercise2-Delete/solution/src/tracker.py

@@ -5,6 +5,30 @@
 def tracker():
     return ExpenseTracker()
 
+def test_add_expense_stores_amount(tracker):
+    tracker.add_expense(50)
+    assert tracker.expenses[0]['amount'] == 50
+
+def test_add_expense_with_category(tracker):
+    tracker.add_expense(10, category="food")
+    assert tracker.expenses[0]['category'] == "food"
+
+def test_list_expenses_by_category_returns_only_requested_category(tracker):
+    # Arrange
+    tracker.add_expense(10.00, category="food")
+    tracker.add_expense(20.00, category="travel")
+    tracker.add_expense(5.00,  category="food")
+
+    # Act
+    results = tracker.list_expenses_by_category("food")
+
+    # Assert
+    assert isinstance(results, list)
+    # Only "food" expenses should be returned
+    assert all(item["category"] == "food" for item in results)
+    # Amounts for the returned items should match the two "food" entries
+    assert sorted(item["amount"] for item in results) == [5.00, 10.00]
+
 def test_delete_expense(tracker):    
     # Arrange: Add an expense to delete
     expense_id = tracker.add_expense(20, "entertainment")

Lesson2-Exercise2-Delete/solution/tests/__init__.py

@@ -1,3 +1,45 @@
-# Purpose of this Folder
+# Exercise: Deleting Expenses
 
-This folder should contain the starter code and instructions for the exercise.
+## Goal
+
+Complete the TDD cycle to implement a `delete_expense` method.
+
+Our expense tracker has Create and Read functionality, now let's add Delete!
+
+Files to work with:
+
+- `tests/test_tracker.py`
+- `src/tracker.py`
+
+## UUIDs
+
+In order to locate a specific expense for deletion, each expense needs to have an identifier (ID). We have already implemented this using Python's built-in `uuid` module.
+
+## Instructions
+
+### Step 1 - Review the Existing Code
+
+The provided code has some more advanced techniques that you may not have encountered before.
+
+`test_tracker.py` uses a pytest **fixture** to avoid repetitive setup code. You do not need to understand fully how this works, but read through the code to see how the `tracker` variable is passed in as an argument to our tests.
+
+`tracker.py` uses the Python `@property` decorator. This allows us to calculate a `total` value whenever this attribute is requested. To external code, the `total` method is indistinguishable from a regular attribute of an `ExpenseTracker` instance.
+
+### Step 2 - Red: Write the Test for Deletion
+
+In `test_tracker.py`, implement `test_delete_expense(tracker)`:
+- The `tracker` has been created using the fixture, so you do not need to instantiate a new `tracker` object
+- Add an expense and capture the ID
+- Call `tracker.delete_expense(expense_id)`
+- Assert `tracker.total` is updated to 0
+- Assert `tracker.get_expense(expense_id)` returns `None`
+
+### Step 3 - Green: Implement Deletion
+
+In `tracker.py`, implement the `delete_expense` method. Use the simplest possible code to pass the test.
+
+Note that you do not need to change any logic in order to retrieve the `total`. If an expense has been removed from the `expenses` list, its amount will automatically be deducted from the total.
+
+### (Optional) Step 4 - Refactor
+
+Think about edge cases, such as attempting to delete a non-existent expense. Should this produce an error? Should it return `None`? Guide your (optional) refactor with tests.

Lesson2-Exercise2-Delete/solution/tests/test_tracker.py

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+

Lesson2-Exercise2-Delete/starter/2.2-Description.md

@@ -1,21 +1,26 @@
+import uuid
+
 class ExpenseTracker:
     def __init__(self):
         self.expenses = []
-        self.total = 0
-        self._next_id = 1
 
-    def add_expense(self, amount, category):
-        expense_id = self._next_id
-        expense = {
-            "id": expense_id,
-            "amount": amount, 
-            "category": category
-        }
+    @property
+    def total(self):
+        return sum([e["amount"] for e in self.expenses])
+
+    # ------------- Create -------------
+    def add_expense(self, amount, category=None):
+        expense_id = str(uuid.uuid4())
+        expense = {"id": expense_id, "amount": amount, "category": category}
         self.expenses.append(expense)
-        self.total += amount
-        self._next_id += 1
         return expense_id
 
+    # ------------- Read -------------
+    def list_expenses_by_category(self, category):
+        return [e for e in self.expenses if e.get("category") == category]
+
     def get_expense(self, expense_id):
-        # Helper to find a specific expense by ID
         return next((e for e in self.expenses if e["id"] == expense_id), None)
+
+
+    # ------------- Delete -------------