From c4acbacdc0f9bfdd5b6a288eef606c0fb1ad76d0 Mon Sep 17 00:00:00 2001
From: SoldatovDaniil <92687673+SoldatovDaniil@users.noreply.github.com>
Date: Tue, 27 Sep 2022 23:04:16 +0300
Subject: [PATCH 1/6] Homework

---
 homeworks/HomeWork2.py | 46 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 homeworks/HomeWork2.py

diff --git a/homeworks/HomeWork2.py b/homeworks/HomeWork2.py
new file mode 100644
index 0000000..e2ccad7
--- /dev/null
+++ b/homeworks/HomeWork2.py
@@ -0,0 +1,46 @@
+class Array(object):
+
+    def __init__(self, *args):
+        self._data = tuple(args)
+
+    def append(self, elem):
+        self._data = (*self._data, elem)
+
+    def __add__(self, other):
+        return Array(*(self._data + other._data))
+
+    def __radd__(self, other):
+        return Array(*(other._data + self._data))
+
+    def show(self):
+        print(self._data)
+
+    def __len__(self):
+        return len(self._data)
+
+    def index(self, elem):
+        if elem in self._data:
+            return self._data.index(elem)
+        else:
+            return -1
+
+    def __getitem__(self, index):
+        return self._data[index]
+
+
+a = Array(1, 2, 123, 56)
+b = Array(1, 1000)
+
+a.show()
+b.show()
+
+a += b
+a = a + b
+b = a + Array(0)
+
+a.show()
+b.show()
+print(a[3])
+
+for i in a:
+    print(i)

From 701ab0df2f89c9646fd40ca2489fda262376d64d Mon Sep 17 00:00:00 2001
From: SoldatovDaniil <92687673+SoldatovDaniil@users.noreply.github.com>
Date: Tue, 27 Sep 2022 23:17:25 +0300
Subject: [PATCH 2/6] Homework

---
 homeworks/{HomeWork2.py => SoldatovDaniil/hw2.py} | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename homeworks/{HomeWork2.py => SoldatovDaniil/hw2.py} (100%)

diff --git a/homeworks/HomeWork2.py b/homeworks/SoldatovDaniil/hw2.py
similarity index 100%
rename from homeworks/HomeWork2.py
rename to homeworks/SoldatovDaniil/hw2.py

From 0385c0ec08f1c165434df7bedbaeb47c9f4c0ff3 Mon Sep 17 00:00:00 2001
From: SoldatovDaniil <92687673+SoldatovDaniil@users.noreply.github.com>
Date: Wed, 28 Sep 2022 20:17:14 +0300
Subject: [PATCH 3/6] add game.py

---
 homeworks/SoldatovDaniil/{ => 2}/hw2.py |  0
 practise/SoldatovDaniil/1/game.py       | 79 +++++++++++++++++++++++++
 2 files changed, 79 insertions(+)
 rename homeworks/SoldatovDaniil/{ => 2}/hw2.py (100%)
 create mode 100644 practise/SoldatovDaniil/1/game.py

diff --git a/homeworks/SoldatovDaniil/hw2.py b/homeworks/SoldatovDaniil/2/hw2.py
similarity index 100%
rename from homeworks/SoldatovDaniil/hw2.py
rename to homeworks/SoldatovDaniil/2/hw2.py
diff --git a/practise/SoldatovDaniil/1/game.py b/practise/SoldatovDaniil/1/game.py
new file mode 100644
index 0000000..c33513c
--- /dev/null
+++ b/practise/SoldatovDaniil/1/game.py
@@ -0,0 +1,79 @@
+# `random` module is used to shuffle field, see:
+# https://docs.python.org/3/library/random.html#random.shuffle
+import random
+
+# Empty tile, there's only one empty cell on a field:
+EMPTY_MARK = 'x'
+
+# Dictionary of possible moves if a form of:
+# key -> delta to move the empty tile on a field.
+MOVES = {
+    'w': -4,
+    's': 4,
+    'a': -1,
+    'd': 1,
+}
+
+
+def shuffle_field():
+    field = []
+    for i in range(1, 16):
+        field.append(i)
+    field.append(EMPTY_MARK)
+    for i in range(100):
+        random.shuffle(field)
+    return field
+
+
+def print_field(field):
+    for i in range(0, 16):
+        if field[i] == EMPTY_MARK or field[i] < 10:
+            print(' ', end='')
+        print(field[i], end=' | ')
+        if i % 4 == 3:
+            print()
+
+
+def is_game_finished(field):
+    for i in range(0, 15):
+        if field[i] != i + 1:
+            return False
+    return True
+
+
+def perform_move(field, key):
+    for i in range(0, 16):
+        if field[i] == EMPTY_MARK:
+            emptyIndex = i
+
+    if emptyIndex % 4 == 3 and key == "d":
+        return None
+    if emptyIndex % 4 == 0 and key == "a":
+        return None
+    if MOVES[key] + emptyIndex < 0 and 15 < MOVES[key] + emptyIndex:
+        return None
+    field[emptyIndex] = field[emptyIndex + MOVES[key]]
+    field[emptyIndex + MOVES[key]] = EMPTY_MARK
+    return field
+
+
+def handle_user_input():
+    userMove = input()
+    if userMove not in ['w', 's', 'a', 'd']:
+        return None
+    return userMove
+
+
+def main():
+    myField = shuffle_field()
+
+    while not(is_game_finished(myField)):
+        print_field(myField)
+        key = handle_user_input()
+        perform_move(myField, key)
+
+
+if __name__ == '__main__':
+    # See what this means:
+    # http://stackoverflow.com/questions/419163/what-does-if-name-main-do
+    main()

From 85a74440d1386235bdea49c8bca5c04abc7a4565 Mon Sep 17 00:00:00 2001
From: SoldatovDaniil <92687673+SoldatovDaniil@users.noreply.github.com>
Date: Mon, 3 Oct 2022 21:57:30 +0300
Subject: [PATCH 4/6] HW3

---
 homeworks/SoldatovDaniil/3/__init__.py |  0
 homeworks/SoldatovDaniil/3/contract.py | 37 +++++++++++
 homeworks/SoldatovDaniil/3/hw4.md      | 85 ++++++++++++++++++++++++++
 3 files changed, 122 insertions(+)
 create mode 100644 homeworks/SoldatovDaniil/3/__init__.py
 create mode 100644 homeworks/SoldatovDaniil/3/contract.py
 create mode 100644 homeworks/SoldatovDaniil/3/hw4.md

diff --git a/homeworks/SoldatovDaniil/3/__init__.py b/homeworks/SoldatovDaniil/3/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/homeworks/SoldatovDaniil/3/contract.py b/homeworks/SoldatovDaniil/3/contract.py
new file mode 100644
index 0000000..475f5fb
--- /dev/null
+++ b/homeworks/SoldatovDaniil/3/contract.py
@@ -0,0 +1,37 @@
+class ContractError(Exception):
+    """We use this error when someone breaks our contract."""
+
+
+#: Special value, that indicates that validation for this type is not required.
+Any = object()
+
+
+def contract(arg_types=None, return_type=None, raises=None):
+    def decorated_contract(func):
+        def wrapped(*args, **kwargs):
+            if arg_types is not None:
+                allArgs = tuple(args + tuple(kwargs.values()))
+                for index in range(len(arg_types)):
+                    if arg_types[index] != Any:
+                        if not isinstance(allArgs[index], arg_types[index]):
+                            raise ContractError("ArgsType Error")
+            try:
+                result = func(*args, **kwargs)
+            except (Exception if raises is None or Any in raises else raises) as ex:
+                raise ex
+            except Exception as ex:
+                raise ContractError from ex
+            if return_type is not None:
+                if not isinstance(result, return_type):
+                    raise ContractError("ReturnType Error")
+            return result
+        return wrapped
+    return decorated_contract
+
+
+@contract(arg_types=(int, int), return_type=float, raises=(ZeroDivisionError,))
+def div(one, two):
+    return one / two
+
+
+print(div(1, 234.5))
diff --git a/homeworks/SoldatovDaniil/3/hw4.md b/homeworks/SoldatovDaniil/3/hw4.md
new file mode 100644
index 0000000..b0a3fc2
--- /dev/null
+++ b/homeworks/SoldatovDaniil/3/hw4.md
@@ -0,0 +1,85 @@
+## Теория
+
+### Exceptions
+
+- `try/except/else/finally`: https://pythonz.net/references/named/try-except-finally/
+- `raise`: https://pythonz.net/references/named/raise/
+- Иерархия Exception: https://docs.python.org/3/library/exceptions.html#exception-hierarchy
+- Когда не нужно использовать Exception? https://sobolevn.me/2019/02/python-exceptions-considered-an-antipattern
+
+### Decorators
+
+- Декораторы шаг за шагом: https://pythonworld.ru/osnovy/dekoratory.html
+
+### Generators
+
+- Iterable vs Iterator vs Generator: https://nvie.com/posts/iterators-vs-generators/
+
+### Comprehensions
+
+- Comprehensions: https://python-3-patterns-idioms-test.readthedocs.io/en/latest/Comprehensions.html
+
+### Context managers
+
+- Менеджеры контекста: https://pythonz.net/references/named/contextmanager/
+- `with`: https://pythonz.net/references/named/with/
+
+
+## Практика
+
+Задача: реализовать декоратор `@contract`. Смотри файл `contract.py`
+
+Требования:
+
+1. Необходимо проверять типы аргументов и тип выходного значения функции. Указываем кортеж типов для `arg_types`. Каждый тип в кортеже - соответсвует типу аргумента. Для типа выходного значения - указываем `return_type`
+
+```python
+@contract(arg_types=(int, int), return_type=int)
+def add_two_numbers(first, second):
+    return first + second
+
+add_two_numbers(1, 2)  # ok
+```
+
+2. Если передан неправильный тип, вызываем ошибку `ContractError`:
+
+```python
+add_two_numbers('a', 'b')  # raises ContractError
+```
+
+3. Параметр `raises` отвечает за типы исключений, которые функция может кидать. Если выкинутое исключение отсутсвует в списке разрешенных, то мы добавляем `ContractError` (смотри `raise from`). Пример:
+
+```python
+@contract(arg_types=(int, int), return_type=float, raises=(ZeroDivisionError,))
+def div(first, second):
+    return first / second
+
+div(1, 2)  # ok
+div(1, 0)  # raises ZeroDisionError
+div(1, None)  # raises ContractError from TypeError
+```
+
+4. Можно не передавать какое-то значение из `arg_types` или `return_type`. Или передать значение `None`: тогда ничего не будет происходить. Пример:
+
+```python
+# validates only return type, args and raises are ignored:
+@contract(return_type=int)
+
+# validation is completely disabled:
+@contract(return_type=None, arg_types=None, raises=None)
+
+# return type and raises checks are disabled:
+@contract(arg_types=(str, str))
+```
+
+5. Можно передать специальное значение `Any` для того, чтобы игнорировать какой-то один тип внутри `arg_types` или `raises`. Например:
+
+```python
+@contract(arg_types=(int, Any))
+def add_two_numbers(first, second):
+    return first + second
+
+add_two_numbers(1, 2)  # ok
+add_two_numbers(1, 3.4)  # ok
+add_two_numbers(2.1, 1)  # raises ContractError
+```

From c21e5328e72533dcb94ac03313d74fd6c27570c8 Mon Sep 17 00:00:00 2001
From: SoldatovDaniil <92687673+SoldatovDaniil@users.noreply.github.com>
Date: Mon, 3 Oct 2022 22:01:10 +0300
Subject: [PATCH 5/6] HW3

---
 homeworks/SoldatovDaniil/3/__init__.py        |  0
 .../SoldatovDaniil/3/{contract.py => hw3.py}  |  0
 homeworks/SoldatovDaniil/3/hw4.md             | 85 -------------------
 3 files changed, 85 deletions(-)
 delete mode 100644 homeworks/SoldatovDaniil/3/__init__.py
 rename homeworks/SoldatovDaniil/3/{contract.py => hw3.py} (100%)
 delete mode 100644 homeworks/SoldatovDaniil/3/hw4.md

diff --git a/homeworks/SoldatovDaniil/3/__init__.py b/homeworks/SoldatovDaniil/3/__init__.py
deleted file mode 100644
index e69de29..0000000
diff --git a/homeworks/SoldatovDaniil/3/contract.py b/homeworks/SoldatovDaniil/3/hw3.py
similarity index 100%
rename from homeworks/SoldatovDaniil/3/contract.py
rename to homeworks/SoldatovDaniil/3/hw3.py
diff --git a/homeworks/SoldatovDaniil/3/hw4.md b/homeworks/SoldatovDaniil/3/hw4.md
deleted file mode 100644
index b0a3fc2..0000000
--- a/homeworks/SoldatovDaniil/3/hw4.md
+++ /dev/null
@@ -1,85 +0,0 @@
-## Теория
-
-### Exceptions
-
-- `try/except/else/finally`: https://pythonz.net/references/named/try-except-finally/
-- `raise`: https://pythonz.net/references/named/raise/
-- Иерархия Exception: https://docs.python.org/3/library/exceptions.html#exception-hierarchy
-- Когда не нужно использовать Exception? https://sobolevn.me/2019/02/python-exceptions-considered-an-antipattern
-
-### Decorators
-
-- Декораторы шаг за шагом: https://pythonworld.ru/osnovy/dekoratory.html
-
-### Generators
-
-- Iterable vs Iterator vs Generator: https://nvie.com/posts/iterators-vs-generators/
-
-### Comprehensions
-
-- Comprehensions: https://python-3-patterns-idioms-test.readthedocs.io/en/latest/Comprehensions.html
-
-### Context managers
-
-- Менеджеры контекста: https://pythonz.net/references/named/contextmanager/
-- `with`: https://pythonz.net/references/named/with/
-
-
-## Практика
-
-Задача: реализовать декоратор `@contract`. Смотри файл `contract.py`
-
-Требования:
-
-1. Необходимо проверять типы аргументов и тип выходного значения функции. Указываем кортеж типов для `arg_types`. Каждый тип в кортеже - соответсвует типу аргумента. Для типа выходного значения - указываем `return_type`
-
-```python
-@contract(arg_types=(int, int), return_type=int)
-def add_two_numbers(first, second):
-    return first + second
-
-add_two_numbers(1, 2)  # ok
-```
-
-2. Если передан неправильный тип, вызываем ошибку `ContractError`:
-
-```python
-add_two_numbers('a', 'b')  # raises ContractError
-```
-
-3. Параметр `raises` отвечает за типы исключений, которые функция может кидать. Если выкинутое исключение отсутсвует в списке разрешенных, то мы добавляем `ContractError` (смотри `raise from`). Пример:
-
-```python
-@contract(arg_types=(int, int), return_type=float, raises=(ZeroDivisionError,))
-def div(first, second):
-    return first / second
-
-div(1, 2)  # ok
-div(1, 0)  # raises ZeroDisionError
-div(1, None)  # raises ContractError from TypeError
-```
-
-4. Можно не передавать какое-то значение из `arg_types` или `return_type`. Или передать значение `None`: тогда ничего не будет происходить. Пример:
-
-```python
-# validates only return type, args and raises are ignored:
-@contract(return_type=int)
-
-# validation is completely disabled:
-@contract(return_type=None, arg_types=None, raises=None)
-
-# return type and raises checks are disabled:
-@contract(arg_types=(str, str))
-```
-
-5. Можно передать специальное значение `Any` для того, чтобы игнорировать какой-то один тип внутри `arg_types` или `raises`. Например:
-
-```python
-@contract(arg_types=(int, Any))
-def add_two_numbers(first, second):
-    return first + second
-
-add_two_numbers(1, 2)  # ok
-add_two_numbers(1, 3.4)  # ok
-add_two_numbers(2.1, 1)  # raises ContractError
-```

From 0eb64c2952099e57ea5b1e1590bafb961b8deddd Mon Sep 17 00:00:00 2001
From: SoldatovDaniil <92687673+SoldatovDaniil@users.noreply.github.com>
Date: Tue, 18 Oct 2022 21:35:51 +0300
Subject: [PATCH 6/6] hw4

---
 homeworks/SoldatovDaniil/4/tests/conftest.py  |   5 +
 .../4/tests/test_done_command.py              |  30 ++++
 .../4/tests/test_representations.py           |  18 +++
 .../4/tests/test_to_read_item.py              |  43 ++++++
 .../4/tests/test_undone_command.py            |  30 ++++
 homeworks/SoldatovDaniil/4/todo/__init__.py   |   0
 homeworks/SoldatovDaniil/4/todo/__main__.py   |  28 ++++
 homeworks/SoldatovDaniil/4/todo/commands.py   | 128 ++++++++++++++++++
 .../4/todo/custom_exceptions.py               |   2 +
 homeworks/SoldatovDaniil/4/todo/models.py     |  52 +++++++
 homeworks/SoldatovDaniil/4/todo/reflection.py |  34 +++++
 homeworks/SoldatovDaniil/4/todo/runtime.py    |  52 +++++++
 homeworks/SoldatovDaniil/4/todo/storage.py    |  21 +++
 13 files changed, 443 insertions(+)
 create mode 100644 homeworks/SoldatovDaniil/4/tests/conftest.py
 create mode 100644 homeworks/SoldatovDaniil/4/tests/test_done_command.py
 create mode 100644 homeworks/SoldatovDaniil/4/tests/test_representations.py
 create mode 100644 homeworks/SoldatovDaniil/4/tests/test_to_read_item.py
 create mode 100644 homeworks/SoldatovDaniil/4/tests/test_undone_command.py
 create mode 100644 homeworks/SoldatovDaniil/4/todo/__init__.py
 create mode 100644 homeworks/SoldatovDaniil/4/todo/__main__.py
 create mode 100644 homeworks/SoldatovDaniil/4/todo/commands.py
 create mode 100644 homeworks/SoldatovDaniil/4/todo/custom_exceptions.py
 create mode 100644 homeworks/SoldatovDaniil/4/todo/models.py
 create mode 100644 homeworks/SoldatovDaniil/4/todo/reflection.py
 create mode 100644 homeworks/SoldatovDaniil/4/todo/runtime.py
 create mode 100644 homeworks/SoldatovDaniil/4/todo/storage.py

diff --git a/homeworks/SoldatovDaniil/4/tests/conftest.py b/homeworks/SoldatovDaniil/4/tests/conftest.py
new file mode 100644
index 0000000..e846edf
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/tests/conftest.py
@@ -0,0 +1,5 @@
+import os
+import sys
+
+BASE_DIR = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
+sys.path.append(BASE_DIR)
diff --git a/homeworks/SoldatovDaniil/4/tests/test_done_command.py b/homeworks/SoldatovDaniil/4/tests/test_done_command.py
new file mode 100644
index 0000000..83a6927
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/tests/test_done_command.py
@@ -0,0 +1,30 @@
+def test_class_exists():
+    from todo.commands import DoneCommand
+
+    assert isinstance(DoneCommand, type)
+
+
+def test_command_label_in_list():
+    from todo.commands import DoneCommand
+    from todo.runtime import get_routes
+
+    assert DoneCommand().label in get_routes()
+
+
+def test_command_execution(monkeypatch):
+    from todo.commands import DoneCommand
+    from todo.runtime import perform_command
+    from todo.models import Storage, ToDoItem
+
+    monkeypatch.setitem(__builtins__, 'input', lambda _: 0)
+
+    item = ToDoItem('test')
+    item.done = False
+
+    s = Storage()
+    s.items.clear()
+    s.items.append(item)
+
+    perform_command(DoneCommand().label)
+
+    assert item.done is True
diff --git a/homeworks/SoldatovDaniil/4/tests/test_representations.py b/homeworks/SoldatovDaniil/4/tests/test_representations.py
new file mode 100644
index 0000000..07043c8
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/tests/test_representations.py
@@ -0,0 +1,18 @@
+def test_to_buy_item():
+    from todo.models import ToBuyItem
+
+    item = ToBuyItem('header', 'price')
+    assert str(item).startswith('- ToBuy: ')
+
+    item.done = True
+    assert str(item).startswith('+ ToBuy: ')
+
+
+def test_to_do_item():
+    from todo.models import ToDoItem
+
+    item = ToDoItem('subject')
+    assert str(item).startswith('- ToDo: ')
+
+    item.done = True
+    assert str(item).startswith('+ ToDo: ')
diff --git a/homeworks/SoldatovDaniil/4/tests/test_to_read_item.py b/homeworks/SoldatovDaniil/4/tests/test_to_read_item.py
new file mode 100644
index 0000000..b1ea1e3
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/tests/test_to_read_item.py
@@ -0,0 +1,43 @@
+def test_class_exists():
+    from todo.models import ToReadItem
+
+    assert isinstance(ToReadItem, type)
+
+
+def test_there_are_attributes():
+    from todo.models import ToReadItem
+
+    heading = 'test'
+    url = 'http://ya.ru'
+    item = ToReadItem(heading, url)
+
+    assert item.heading == heading
+    assert item.url == url
+    assert item.done is False
+
+
+def test_fabric_method(monkeypatch):
+    from todo.models import ToReadItem
+
+    value = 'some input'
+
+    monkeypatch.setitem(__builtins__, 'input', lambda _: value)
+    item = ToReadItem.construct()
+
+    assert item.heading == value
+    assert item.url == value
+    assert item.done is False
+
+
+def test_representation():
+    from todo.models import ToReadItem
+
+    heading = 'test'
+    url = 'http://ya.ru'
+    item = ToReadItem(heading, url)
+
+    assert str(item) == '- ToRead: {} {}'.format(heading, url)
+
+    item.done = True
+
+    assert str(item) == '+ ToRead: {} {}'.format(heading, url)
diff --git a/homeworks/SoldatovDaniil/4/tests/test_undone_command.py b/homeworks/SoldatovDaniil/4/tests/test_undone_command.py
new file mode 100644
index 0000000..b25bedf
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/tests/test_undone_command.py
@@ -0,0 +1,30 @@
+def test_class_exists():
+    from todo.commands import UndoneCommand
+
+    assert isinstance(UndoneCommand, type)
+
+
+def test_command_label_in_list():
+    from todo.commands import UndoneCommand
+    from todo.runtime import get_routes
+
+    assert UndoneCommand().label in get_routes()
+
+
+def test_command_execution(monkeypatch):
+    from todo.commands import UndoneCommand
+    from todo.runtime import perform_command
+    from todo.models import Storage, ToDoItem
+
+    monkeypatch.setitem(__builtins__, 'input', lambda _: 0)
+
+    item = ToDoItem('test')
+    item.done = True
+
+    s = Storage()
+    s.items.clear()
+    s.items.append(item)
+
+    perform_command(UndoneCommand().label)
+
+    assert item.done is False
diff --git a/homeworks/SoldatovDaniil/4/todo/__init__.py b/homeworks/SoldatovDaniil/4/todo/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/homeworks/SoldatovDaniil/4/todo/__main__.py b/homeworks/SoldatovDaniil/4/todo/__main__.py
new file mode 100644
index 0000000..55f9f2c
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/todo/__main__.py
@@ -0,0 +1,28 @@
+"""
+Main file. Contains program execution logic.
+"""
+
+from todo.custom_exceptions import UserExitException
+from todo.runtime import parse_user_input, perform_command
+
+
+def main():
+    """
+    Main method, works infinitely until user runs `exit` command.
+    Or hits `Ctrl+C` in the console.
+    """
+    while True:
+        try:
+            perform_command(parse_user_input())
+        except UserExitException:
+            break
+        except Exception as ex:
+            print('You have done something wrong!', ex)
+
+
+if __name__ == '__main__':
+    try:
+        main()
+    except KeyboardInterrupt:
+        print()
+        print('Shutting down, bye!')
diff --git a/homeworks/SoldatovDaniil/4/todo/commands.py b/homeworks/SoldatovDaniil/4/todo/commands.py
new file mode 100644
index 0000000..e331c06
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/todo/commands.py
@@ -0,0 +1,128 @@
+
+from todo.custom_exceptions import UserExitException
+from todo.models import BaseItem
+from todo.reflection import find_classes
+
+
+class BaseCommand(object):
+    label: str
+
+    def perform(self, store):
+        raise NotImplementedError()
+
+
+class ListCommand(BaseCommand):
+    label = 'list'
+
+    def perform(self, store):
+        if len(store.items) == 0:
+            print('There are no items in the storage.')
+            return
+
+        for index, obj in enumerate(store.items):
+            print('{0}: {1}'.format(index, str(obj)))
+
+
+class NewCommand(BaseCommand):
+    label = 'new'
+
+    def perform(self, store):
+        classes = self._load_item_classes()
+
+        print('Select item type:')
+        for index, name in enumerate(classes.keys()):
+            print('{0}: {1}'.format(index, name))
+
+        selection = None
+        selected_key = None
+
+        while True:
+            try:
+                selected_key = self._select_item(classes)
+            except ValueError:
+                print('Bad input, try again.')
+            except IndexError:
+                print('Wrong index, try again.')
+            else:
+                break
+
+        selected_class = classes[selected_key]
+        print('Selected: {0}'.format(selected_class.__name__))
+        print()
+
+        new_object = selected_class.construct()
+
+        store.items.append(new_object)
+        print('Added {0}'.format(str(new_object)))
+        print()
+        return new_object
+
+    def _load_item_classes(self) -> dict:
+        # Dynamic load:
+        return dict(find_classes(BaseItem))
+
+    def _select_item(self, classes):
+        selection = int(input('Input number: '))
+        if selection < 0:
+            raise IndexError('Index needs to be >0')
+        return list(classes.keys())[selection]
+
+
+class MarkCommand(object):
+
+    def perform(self, store):
+        x = 0
+
+        for obj in store.items:
+            if str(obj)[0] == self.char_command:
+                x += 1
+        if x == 0:
+            print("There are no {0} items in the storage.".format(self.char_command))
+            return
+
+        for index, obj in enumerate(store.items):
+            if str(obj)[0] == self.char_command:
+                print('{0}: {1}'.format(index, str(obj)))
+
+        selected_item = self.select_item(store)
+
+        print("{0} has been {1}\n".format(selected_item, self.operation))
+
+        operation = getattr(selected_item, str(self.operation), None)
+        assert operation is not None
+        operation()
+
+    def select_item(self, store):
+        while True:
+            try:
+                user_selection = int(input("Input number of item: "))
+                if user_selection < 0 or str(store.items[user_selection])[0] != self.char_command:
+                    raise IndexError()
+            except ValueError:
+                print("Bad input")
+            except IndexError:
+                print("Bad index")
+            else:
+                break
+        if store.items is None:
+            print("There are no items in storage")
+        return store.items[user_selection]
+
+
+class DoneCommand(MarkCommand, BaseCommand):
+    label = "done"
+    char_command = '-'
+    operation = "mark_done"
+
+
+class UndoneCommand(MarkCommand, BaseCommand):
+    label = "undone"
+    char_command = '+'
+    operation = "mark_undone"
+
+
+class ExitCommand(BaseCommand):
+    label = 'exit'
+
+    def perform(self, _store):
+        raise UserExitException('See you next time!')
diff --git a/homeworks/SoldatovDaniil/4/todo/custom_exceptions.py b/homeworks/SoldatovDaniil/4/todo/custom_exceptions.py
new file mode 100644
index 0000000..5e8963c
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/todo/custom_exceptions.py
@@ -0,0 +1,2 @@
+class UserExitException(Exception):
+    """We use this exception when user wants to exit."""
diff --git a/homeworks/SoldatovDaniil/4/todo/models.py b/homeworks/SoldatovDaniil/4/todo/models.py
new file mode 100644
index 0000000..8a4f40b
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/todo/models.py
@@ -0,0 +1,52 @@
+class BaseItem(object):
+    def __init__(self, heading):
+        self.heading = heading
+        self.done = False  # TODO: make sure we can use it...
+
+    def __repr__(self):
+        return self.__class__.__name__
+
+    def mark_done(self):
+        self.done = True
+
+    def mark_undone(self):
+        self.done = False
+
+    def __str__(self):
+        return "{0} {1}".format('+' if self.done else '-', self.__repr__())
+
+    @classmethod
+    def construct(cls):
+        raise NotImplementedError()
+
+
+class ToDoItem(BaseItem):
+    def __str__(self):
+        return '{0}: {1}'.format(
+            super().__str__(self),
+            self.heading,
+        )
+
+    @classmethod
+    def construct(cls):
+        heading = input('Input heading: ')
+        return cls(heading)
+
+
+class ToBuyItem(BaseItem):
+    def __init__(self, heading, price):
+        super().__init__(heading)
+        self.price = price
+
+    def __str__(self):
+        return '{0}: {1} for {2}'.format(
+            super().__str__(self),
+            self.heading,
+            self.price,
+        )
+
+    @classmethod
+    def construct(cls):
+        heading = input('Input heading: ')
+        price = input('Input price: ')
+        return cls(heading, price)
diff --git a/homeworks/SoldatovDaniil/4/todo/reflection.py b/homeworks/SoldatovDaniil/4/todo/reflection.py
new file mode 100644
index 0000000..dee9f85
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/todo/reflection.py
@@ -0,0 +1,34 @@
+import inspect
+import sys
+
+
+def find_classes(base_class) -> tuple:
+    """
+    Finds all subclasses of a class inside module.
+
+    :param base_class: Base class to search children.
+    :return: tuple of subclasses
+    """
+    return inspect.getmembers(
+        sys.modules[base_class.__module__],
+        _reflect_filter(base_class),
+    )
+
+
+def _reflect_filter(base_class):
+    """
+    Reflection is used to load modules dynamically.
+
+    This method is complex. It does some dark magic.
+    How is it even possible to understand it?
+
+    :param base_class: Target base class
+    :return: function to filter only subclasses of `base_class`
+    """
+    def class_filter(klass):
+        return inspect.isclass(
+            klass,
+        ) and klass.__module__ == base_class.__module__ and issubclass(
+            klass, base_class,
+        ) and klass is not base_class
+    return class_filter
diff --git a/homeworks/SoldatovDaniil/4/todo/runtime.py b/homeworks/SoldatovDaniil/4/todo/runtime.py
new file mode 100644
index 0000000..c955fa3
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/todo/runtime.py
@@ -0,0 +1,52 @@
+from todo.commands import BaseCommand
+from todo.custom_exceptions import UserExitException
+from todo.reflection import find_classes
+from todo.storage import Storage
+
+
+def get_routes() -> dict:
+    """
+    This function contains the dictionary of possible commands.
+    :return: `dict` of possible commands, with the format: `name -> class`
+    """
+    routes = find_classes(BaseCommand)
+    return {
+        route().label: route
+        for _, route in routes
+    }
+
+
+def perform_command(command: str) -> None:
+    """
+    Performs the command by name.
+    Stores the result in `Storage()`.
+    :param command: command name, selected by user.
+    """
+    command = command.lower()
+    routes = get_routes()
+
+    try:
+        command_class = routes[command]
+    except KeyError:
+        print('Bad command, try again.')
+        return
+
+    command_inst = command_class()
+    storage = Storage()
+
+    try:
+        command_inst.perform(storage)
+    except UserExitException as ex:
+        # Handling `exit` command.
+        print(ex)
+        raise
+
+
+def parse_user_input():
+    """
+    Gets the user input.
+    :return: `str` with the user input.
+    """
+    commands = get_routes().keys()
+    message = 'Input your command: ({0}): '.format('|'.join(commands))
+    return input(message)
diff --git a/homeworks/SoldatovDaniil/4/todo/storage.py b/homeworks/SoldatovDaniil/4/todo/storage.py
new file mode 100644
index 0000000..ef58690
--- /dev/null
+++ b/homeworks/SoldatovDaniil/4/todo/storage.py
@@ -0,0 +1,21 @@
+class Storage(object):  # storage = Storge()
+    """
+    Singleton storage.
+
+    Read more about singleton design pattern:
+    https://stackoverflow.com/questions/6760685/creating-a-singleton-in-python
+    https://en.wikipedia.org/wiki/Singleton_pattern
+
+    It is used to emulate in-memory storage.
+    It should be replaced with a database in a real application.
+    """
+
+    obj = None
+    items = None
+
+    @classmethod
+    def __new__(cls, *args):
+        if cls.obj is None:
+            cls.obj = object.__new__(cls)
+            cls.items = []
+        return cls.obj