What is the __del__ method and when to use it?

Question

Accepted Answer

**__del__** is called when an object is **about to be destroyed**. Use sparingly — it's unreliable.

```python
class TempFile:
    def __init__(self, filename):
        self.filename = filename
        self.file = open(filename, "w")

def write(self, data):
        self.file.write(data)

def __del__(self):
        # NOT guaranteed to be called!
        self.file.close()
        os.remove(self.filename)
        print(f"Cleaned up {self.filename}")
```

**Problems with __del__:**
- **Not guaranteed** to be called.
- Order of destruction is undefined.
- Circular references may prevent calling.
- Reference counting vs GC timing.

**Better alternatives:**
- **Context managers** (`with` statement).
- **weakref.finalize** — more reliable.
- **atexit** — for program exit cleanup.

```python
import weakref

class TempFile:
    def __init__(self, filename):
        self.filename = filename
        self.file = open(filename, "w")
        weakref.finalize(self, self._cleanup, filename)

@staticmethod
    def _cleanup(filename):
        os.remove(filename)
```

Python: What is the del method and when to use it?