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ExitStack

Learn dynamic context management with ExitStack.

ExitStack

ExitStack dynamically manages multiple context managers. It is ideal when the number is not known in advance:

from contextlib import ExitStack

with ExitStack() as stack:
    stack.callback(print, "bitti")
    print("içeride")
# bitti

Here stack.callback(print, "bitti") schedules a print("bitti") call at block end. ExitStack runs all callbacks in reverse order.

This is a flexible tool for dynamic cleanup.

callback and enter_context

ExitStack offers two main methods. callback(fn, *args) schedules a function call at block end. enter_context(cm) adds a context manager to the ExitStack:

with ExitStack() as stack:
    stack.callback(print, "temizlik")
    f = stack.enter_context(open("dosya.txt"))

Cleanup happens in reverse order of addition — last added is closed first. This ensures safe management of multiple resources.

This is standard for dynamic resource management.

Practice Schedule a callback with ExitStack

Write from contextlib import ExitStack. Inside a with ExitStack() as stack: block write stack.callback(print, "bitti") and print("içeride").

Starter code

main.py
# import ExitStack
# schedule cleanup with callback

Sample solution

main.py
from contextlib import ExitStack

with ExitStack() as stack:
    stack.callback(print, "bitti")
    print("içeride")

Expected output

içeride
bitti

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Complete the ExitStack import

Question 
from contextlib import ____

with ExitStack() as stack:
    stack.callback(print, "bitti")
Answer 
from contextlib import ExitStack

with ExitStack() as stack:
    stack.callback(print, "bitti")

Explanation: ExitStack comes from the contextlib module.

2 In which order does ExitStack run callbacks?

  • Randomly
  • In addition order
  • In reverse order Correct answer
  • Only the first

Explanation: ExitStack runs callbacks in reverse order (LIFO).

3 Match ExitStack concepts

Term Meaning
ExitStack Dynamic manager
callback Schedules cleanup
enter_context Adds a cm
reverse order Closing order

All lessons in Intermediate

1 Classes

  1. class
  2. Attributes
  3. Methods
  4. __init__
  5. __str__ and __repr__
  6. Summary - Classes

2 Inheritance

  1. Inheritance basics
  2. super()
  3. Method overriding
  4. Multiple inheritance
  5. isinstance and issubclass
  6. Summary - Inheritance

3 Project: Helper library

  1. Class design
  2. String helpers
  3. Number helpers
  4. Date helpers
  5. Putting it together

4 Encapsulation

  1. Private attributes
  2. @property
  3. @x.setter
  4. @dataclass
  5. __slots__
  6. Summary - Encapsulation

5 Static and class methods

  1. @staticmethod
  2. @classmethod
  3. Factory pattern
  4. Class variables
  5. Constants
  6. Summary - Static and class methods

6 Magic methods

  1. __eq__ and __lt__
  2. __add__
  3. __len__ and __getitem__
  4. __iter__ and __next__
  5. __contains__
  6. Summary - Magic methods

7 Property and decorator

  1. Decorator basics
  2. Function decorator
  3. @property details
  4. @cached_property
  5. functools.wraps
  6. Summary - Property and decorator

8 Project: Quiz app

  1. Quiz model
  2. Adding questions
  3. Running the quiz
  4. Score calculation
  5. Putting it together

9 Abstract classes

  1. ABC
  2. @abstractmethod
  3. Abstract property
  4. Protocol
  5. Interface vs abstract
  6. Summary - Abstract classes

10 Dataclasses

  1. @dataclass basics
  2. field()
  3. frozen
  4. __post_init__
  5. asdict and astuple
  6. Summary - Dataclasses

11 Project: Blog app

  1. Model design
  2. Blog class
  3. Adding comments
  4. Search and filter
  5. Putting it together

12 File I/O

  1. open
  2. read and readline
  3. write and writelines
  4. with statement
  5. File modes
  6. Summary - File I/O

13 CSV and JSON

  1. csv.reader
  2. csv.writer
  3. DictReader and DictWriter
  4. json.load and dump
  5. json.loads and dumps
  6. Summary - CSV and JSON

14 Pathlib

  1. Path
  2. / operator
  3. exists and is_file
  4. mkdir and rmdir
  5. glob and rglob
  6. Summary - Pathlib

15 Advanced exceptions

  1. Multiple except
  2. except tuple
  3. Exception chaining
  4. except as
  5. traceback
  6. Summary - Advanced exceptions

16 Collections module

  1. Counter
  2. defaultdict
  3. OrderedDict
  4. deque
  5. namedtuple
  6. Summary - Collections

17 Itertools

  1. chain
  2. count and cycle
  3. islice
  4. combinations and permutations
  5. groupby
  6. Summary - Itertools

18 Generators

  1. yield
  2. Generator object
  3. yield from
  4. send and throw
  5. close
  6. Summary - Generators

19 Context managers

  1. with statement
  2. __enter__ and __exit__
  3. @contextmanager
  4. Catching exceptions
  5. ExitStack
  6. Summary - Context managers

20 Intermediate final

  1. Project design
  2. OOP model
  3. Generator layer
  4. File I/O
  5. Putting it together