Need to let someone edit a task, then save or cancel? Keep the original task and make a separate object for the proposed changes. Copy the instance itself—not just its `__dict__`—so the working copy remains a `Task` with its class’s methods. section 10.3 section 10.3.1
from copy import copy
task_copied = copy(task)
print(task_copied)
# output: Task('Homework', 'Math and physics')
`copy(task)` creates a `Task` instance with the same displayed data. It is a shallow copy. section 10.3.1
A shallow copy does not make separate copies of interior mutable objects. If a task has a `tags` list, `task_copied.tags.append("red")` also changes the tags visible through the original task: both instances refer to the same list. Check that relationship with `task.tags is task_copied.tags`; `is` tests object identity, while `==` tests value equality. section 10.3.2
Choose the copying behavior to match what may change:
- Use `copy(task)` when sharing interior mutable objects is acceptable; a shallow copy can save memory. section 10.3.1 section 10.3.4
- Use `deepcopy(task)` when edits to contained mutable objects must leave the original data intact. section 10.3.5 section 10.3.4
- For a custom class that needs special behavior, define `__copy__` or `__deepcopy__`. For example, a custom `__copy__` could prefix the copied task’s title and create a new tags list. section 10.3.5
Object copying is distinct from copying a file. To keep a source file and place a second file at a destination path, use `shutil.copy(src, dst)`. section 11.4.4
