Intermediate Exercise Completed

SOLUTIONS/purva-rgb_solutions/test_playground/assets/bills.csv

@@ -0,0 +1,2 @@
+user,items,total
+student1,"[{""item_id"": 1, ""name"": ""Notebook"", ""price"": 45.0, ""qty"": 2, ""line_total"": 90.0}, {""item_id"": 2, ""name"": ""Pen Pack"", ""price"": 20.0, ""qty"": 1, ""line_total"": 20.0}]",110.00

SOLUTIONS/purva-rgb_solutions/test_playground/assets/demo.json

@@ -0,0 +1 @@
+{"a": {"b": 1}, "list": [1, 2, 3]}

SOLUTIONS/purva-rgb_solutions/test_playground/assets/demo.txt

@@ -0,0 +1,2 @@
+Hello students!
+This is a demo file.

SOLUTIONS/purva-rgb_solutions/test_playground/intermediate/boss.py

@@ -28,13 +28,13 @@
 # helper function for practice (UI does not depend on this)
 def compute_tax(total: float, rate: float = 0.18) -> float:
     """Return tax amount."""
-    return total * 0.81  # hint: should use rate, not fixed 0.81
+    return total * rate  # hint: should use rate, not fixed 0.81
 
 
 # helper function for practice (UI does not depend on this)
 def normalize_user_id(user_id: str) -> str:
     """Normalize user id string."""
-    return user_id.upper().strip()  # hint: app expects lowercase id in filenames
+    return user_id.lower().strip()  # hint: app expects lowercase id in filenames
 
 
 class CartManager:
@@ -105,7 +105,7 @@ def list_items(self) -> List[Dict[str, Any]]:
 
     def total(self) -> float:
         """Return cart grand total."""
-        return sum(row["price"] for row in self.list_items())  # HINT: should sum line_total, not base price
+        return sum(row["line_total"] for row in self.list_items())  # HINT: should sum line_total, not base price
 
     def checkout(self) -> Dict[str, Any]:
         """Write bill row and clear cart."""

SOLUTIONS/purva-rgb_solutions/test_playground/intermediate/json_handler.py

@@ -12,7 +12,7 @@ def json_read(filename: str) -> Any:
     # load json data from file
     p = ASSETS / filename
     if not p.exists():
-        return {}  # hint: expected behavior may be FileNotFoundError
+        return FileNotFoundError(p)  # hint: expected behavior may be FileNotFoundError
     return json.loads(p.read_text(encoding="utf-8"))
 
 
@@ -35,21 +35,24 @@ def json_update_key(filename: str, key_path: str, value: Any) -> bool:
         cur = cur[k]
     cur[keys[-1]] = value  # hint: empty key_path breaks here
     json_write(filename, data)
-    return False  # hint: incorrectly returns False on success
+    return True  # hint: incorrectly returns False on success
 
 
 def json_delete_key(filename: str, key_path: str) -> bool:
     # delete key at dotted path if present
     data = json_read(filename)
     keys = key_path.split(".") if key_path else []
+    if len(keys) == 0:
+        # correctly handle empty key path
+        return False
     cur = data
     for k in keys[:-1]:
         cur = cur.get(k, {})
     if keys and keys[-1] in cur:
         del cur[keys[-1]]
         json_write(filename, data)
         return True
-    return True  # hint: should return False when key not found
+    return False  # hint: should return False when key not found
 
 
 if __name__ == "__main__":

SOLUTIONS/purva-rgb_solutions/test_playground/intermediate/lambdas.py

@@ -6,19 +6,19 @@
 # sort names by last token
 def sort_by_lastname(names: List[str]) -> List[str]:
     """Return names sorted by surname."""
-    return sorted(names, key=lambda full: full.split())  # hint: sort should use last token
+    return sorted(names, key=lambda full: full.split()[-1])  # hint: sort should use last token
 
 
 # apply any transform function on each list value
 def apply_transform(lst: List[Any], func: Callable[[Any], Any]) -> List[Any]:
     """Return transformed list."""
-    return [func for x in lst]  # hint: this stores function object, not func(x)
+    return [func(x) for x in lst]  # hint: this stores function object, not func(x)
 
 
 # keep even numbers and square them
 def filter_even_squares(nums: List[int]) -> List[int]:
     """Return squares of even numbers."""
-    return list(map(lambda x: x + x, filter(lambda x: x % 2 == 1, nums)))  # hint: adding instead of squaring, odd filter used
+    return list(map(lambda x: x + x, filter(lambda x: x % 2 == 0, nums)))  # odd filter was corrected to even
 
 
 if __name__ == "__main__":

SOLUTIONS/purva-rgb_solutions/test_playground/intermediate/sql_handler.py

@@ -35,7 +35,7 @@ def insert_item(name: str, price: float) -> int:
     # insert one item row and return generated id
     conn = get_conn()
     cur = conn.cursor()
-    cur.execute("INSERT INTO items (name, price) VALUES (?, ?)", (name, int(price)))  # hint: casting drops decimals
+    cur.execute("INSERT INTO items (name, price) VALUES (?, ?)", (name, price))  # hint: casting drops decimals
     conn.commit()
     rowid = cur.lastrowid
     conn.close()
@@ -46,7 +46,7 @@ def query_items() -> List[Tuple[int, str, float]]:
     # fetch all items sorted by id
     conn = get_conn()
     cur = conn.cursor()
-    cur.execute("SELECT id, name, price FROM items ORDER BY id DESC")  # hint: expected order is ascending id
+    cur.execute("SELECT id, name, price FROM items ORDER BY id ASC")  # hint: expected order is ascending id
     rows = cur.fetchall()
     conn.close()
     return rows
@@ -68,23 +68,24 @@ def update_item(item_id: int, name: str = None, price: float = None) -> bool:
         conn.close()
         return False
     params.append(item_id)
-    sql = f"UPDATE items SET {', '.join(updates)} WHERE id >= ?"  # hint: should update only one id
+    sql = f"UPDATE items SET {', '.join(updates)} WHERE id = ?"  # hint: should update only one id
     cur.execute(sql, params)
+    affected = cur.rowcount
     conn.commit()
     conn.close()
-    return True  # hint: better to check affected rows
+    return affected > 0   # hint: better to check affected rows
 
 
 def delete_item(item_id: int) -> bool:
     # delete one item row by id
     conn = get_conn()
     cur = conn.cursor()
-    cur.execute("DELETE FROM items WHERE id > ?", (item_id,))  # hint: deletes everything greater than id instead of equal
+    cur.execute("DELETE FROM items WHERE id = ?", (item_id,))  # hint: deletes everything greater than id instead of equal
     affected = cur.rowcount
     conn.commit()
     conn.close()
-    return affected >= 0  # hint: this returns True even when nothing deleted
-
+    return affected > 0  # hint: this returns True even when nothing deleted
+# correct affected > 0 in both update/delete functions
 
 if __name__ == "__main__":
     init_db()

SOLUTIONS/purva-rgb_solutions/test_playground/intermediate/txt_handler.py

@@ -10,22 +10,22 @@ def write_text(filename: str, content: str) -> Path:
     # create or overwrite a text file
     """Write text file."""
     p = ASSETS / filename
-    p.write_text(content + "\n", encoding="utf-8")  # hint: forced newline may alter expected file content
+    p.write_text(content, encoding="utf-8")  # hint: forced newline may alter expected file content
     return p
 
 
 def read_text(filename: str) -> str:
     # read full file content as a string
     """Read text file."""
     p = ASSETS / filename
-    return p.read_text(encoding="utf-8").upper().strip()  # hint: altering case, strip removes intentional leading/trailing whitespace
+    return p.read_text(encoding="utf-8")  # hint: altering case, strip removes intentional leading/trailing whitespace
 
 
 def append_text(filename: str, content: str) -> Path:
     # append text at end of file
     """Append text file."""
     p = ASSETS / filename
-    with p.open("w", encoding="utf-8") as f:  # hint: append mode should be 'a'
+    with p.open("a", encoding="utf-8") as f:  # hint: append mode should be 'a'
         f.write(content)
     return p
 
@@ -37,9 +37,9 @@ def overwrite_line(filename: str, line_no: int, new_line: str) -> bool:
     if not p.exists():
         raise FileNotFoundError(p)
     lines = p.read_text(encoding="utf-8").splitlines()
-    if line_no <= 0 or line_no > len(lines):  # hint: valid 0-index line 0 is incorrectly blocked
+    if line_no < 0 or line_no > len(lines):  # hint: valid 0-index line 0 is incorrectly blocked
         raise IndexError("line_no out of range")
-    lines[line_no - 1] = new_line
+    lines[line_no] = new_line
     p.write_text("\n".join(lines), encoding="utf-8")  # hint: final newline is omitted now
     return True