Basics

Object Lifecycle

Names keep objects reachable until the last reference goes away.

Two names can refer to the same object. Mutating through one name would affect the object seen through the other.

Source

class Box:
    def __init__(self, label):
        self.label = label

box = Box("draft")
alias = box

print(box is alias)
print(alias.label)

Output

True
draft

Rebinding box does not change the original object. alias still reaches the first Box until that reference is removed too.

Source

box = Box("published")
print(alias.label)
print(box.label)

del alias
print("old object unreachable")

Output

draft
published
old object unreachable

Notes

Assignment binds names to objects; it does not copy the object.
del name removes one reference, not necessarily the object itself.
Python reclaims unreachable objects automatically, so lifetime bugs usually come from keeping references longer than intended.

Run the complete example

True
draft
draft
published
old object unreachable

Execution time appears here after you run the example.