del — Intermediate Examples

Deletes a variable, list item, dictionary entry, or object attribute

EasyIntermediateAdvancedExpert

del with slices and attributes

Advanced deletion targets.

python
# Delete a slice
nums = list(range(10))
del nums[2:5]
print(nums)

# Delete every other element
nums = list(range(10))
del nums[::2]
print(nums)

# Delete object attributes
class Config:
    def __init__(self):
        self.debug = True
        self.verbose = True
        self.port = 8080

cfg = Config()
print(vars(cfg))
del cfg.debug
print(vars(cfg))

# del with __delitem__
class SafeDict(dict):
    def __delitem__(self, key):
        if key.startswith("_"):
            raise KeyError(f"Cannot delete private key: {key}")
        super().__delitem__(key)

d = SafeDict({"name": "Alice", "_id": 1})
del d["name"]
try:
    del d["_id"]
except KeyError as e:
    print(f"Protected: {e}")
print(d)
Expected Output
[0, 1, 5, 6, 7, 8, 9]
[1, 3, 5, 7, 9]
{'debug': True, 'verbose': True, 'port': 8080}
{'verbose': True, 'port': 8080}
Protected: 'Cannot delete private key: _id'
{'_id': 1}

del can target slices, object attributes, and dict keys. Custom classes can control deletion behavior via __delitem__ and __delattr__.

del and garbage collection

Understanding what del actually does.

python
import sys

# del removes the reference, not the object
a = [1, 2, 3]
b = a  # b is another reference
print(f"refcount before del: {sys.getrefcount(a) - 1}")

del a  # removes name 'a', but object still exists via 'b'
print(f"b still works: {b}")

# Object is garbage collected when refcount reaches 0
class Tracked:
    def __init__(self, name):
        self.name = name
    def __del__(self):
        print(f"  {self.name} garbage collected")

print("Creating objects:")
t1 = Tracked("first")
t2 = Tracked("second")
print("Deleting first:")
del t1
print("Deleting second:")
del t2
print("Done")

del removes a name binding (reference), not the object itself. The object is garbage collected when its reference count reaches 0.

Want to try these examples interactively?

Open Intermediate Playground
← Easy ExamplesAdvanced Examples →