From 734973bdac93586ed9601800b503a3a6ad27d202 Mon Sep 17 00:00:00 2001 From: Elena Krivchanskaya Date: Thu, 24 Sep 2026 00:45:16 +0300 Subject: [PATCH 1/7] Update constants.py first task 25.09.2026 --- src/part1/constants.py | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/src/part1/constants.py b/src/part1/constants.py index 9abfbba2..31d4b766 100644 --- a/src/part1/constants.py +++ b/src/part1/constants.py @@ -19,20 +19,20 @@ # Все константы, зависящие от ёмкостей *_BITS, должны вычисляться из них. # Twitter's original Snowflake epoch: 2010-11-04 01:42:54.657 UTC. -EPOCH_MS_DEFAULT: Final[int] = 0 +EPOCH_MS_DEFAULT: Final[int] = 1288834974657 # Node identifier used when the caller does not supply one. -NODE_ID_DEFAULT: Final[int] = 0 +NODE_ID_DEFAULT: Final[int] = 1 # Width of each field, in bits. -TIMESTAMP_BITS: Final[int] = 0 -NODE_ID_BITS: Final[int] = 0 -SEQUENCE_ID_BITS: Final[int] = 0 +TIMESTAMP_BITS: Final[int] = 41 +NODE_ID_BITS: Final[int] = 10 +SEQUENCE_ID_BITS: Final[int] = 12 # Largest value each field can hold. -TIMESTAMP_MS_MAX: Final[int] = 0 -NODE_ID_MAX: Final[int] = 0 -SEQUENCE_ID_MAX: Final[int] = 0 +TIMESTAMP_MS_MAX: Final[int] = 2**41 +NODE_ID_MAX: Final[int] = 2**10 +SEQUENCE_ID_MAX: Final[int] = 2**12 # Здесь можно добавить собственные вспомогательные константы # (например, сдвиги полей при сборке идентификатора). From 8b1ac7b9ba49552b1984fc9770071e2baaecf110 Mon Sep 17 00:00:00 2001 From: Elena Krivchanskaya Date: Thu, 24 Sep 2026 00:45:36 +0300 Subject: [PATCH 2/7] Update snowflake.py first task 25.09.2026 --- src/part1/snowflake.py | 100 +++++++++++------------------------------ 1 file changed, 27 insertions(+), 73 deletions(-) diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py index d3abf050..858d4b0e 100644 --- a/src/part1/snowflake.py +++ b/src/part1/snowflake.py @@ -13,73 +13,37 @@ :func:`decode_node_id` and :func:`decode_sequence_id`. """ -import time # noqa: F401 +import time -from .constants import ( # noqa: F401 +from .constants import ( EPOCH_MS_DEFAULT, + NODE_ID_BITS, NODE_ID_DEFAULT, NODE_ID_MAX, + SEQUENCE_ID_BITS, SEQUENCE_ID_MAX, + TIMESTAMP_BITS, TIMESTAMP_MS_MAX, ) def read_current_millis(epoch_ms: int) -> int: - """Read the number of milliseconds elapsed since the custom epoch. - - Args: - epoch_ms: The custom epoch expressed as Unix milliseconds. - - Returns: - The count of whole milliseconds between ``epoch_ms`` and now. May be - negative if ``epoch_ms`` lies in the future. - """ - # TODO: реализуйте функцию - return 0 + return time.time() - epoch_ms - EPOCH_MS_DEFAULT def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int: - """Read the timestamp field out of a Snowflake identifier. - - Args: - snowflake_id: An identifier produced against the same epoch. - epoch_ms: The epoch the identifier was generated against. Defaults to - the original Twitter epoch (2010-11-04 01:42:54.657 UTC). - - Returns: - The absolute Unix time in milliseconds at which the identifier was - generated. - """ - # TODO: реализуйте функцию - return 0 + creation_time = (snowflake_id >> SEQUENCE_ID_BITS >> NODE_ID_BITS) & ( + (1 << TIMESTAMP_BITS) - 1 + ) + return creation_time + epoch_ms def decode_node_id(snowflake_id: int) -> int: - """Read the node identifier field out of a Snowflake identifier. - - Args: - snowflake_id: An identifier produced by :func:`generate_snowflake_id`. - - Returns: - The node identifier packed into ``snowflake_id``, in the range - ``[0, NODE_ID_MAX]``. - """ - # TODO: реализуйте функцию - return 0 + return (snowflake_id >> SEQUENCE_ID_BITS) & ((1 << NODE_ID_BITS) - 1) def decode_sequence_id(snowflake_id: int) -> int: - """Read the sequence counter field out of a Snowflake identifier. - - Args: - snowflake_id: An identifier produced by :func:`generate_snowflake_id`. - - Returns: - The per-millisecond sequence counter packed into ``snowflake_id``, in - the range ``[0, SEQUENCE_ID_MAX]``. - """ - # TODO: реализуйте функцию - return 0 + return (snowflake_id) & ((1 << SEQUENCE_ID_BITS) - 1) def generate_snowflake_id( @@ -87,28 +51,18 @@ def generate_snowflake_id( node_id: int = NODE_ID_DEFAULT, epoch_ms: int = EPOCH_MS_DEFAULT, ) -> int | None: - """Build and return a Snowflake identifier for the current millisecond. - - The function is stateless: the caller passes the per-millisecond sequence - counter explicitly. It is the caller's responsibility to increment - ``sequence_id`` for identifiers minted within the same millisecond and to - reset it once the clock advances. - - Args: - sequence_id: The per-millisecond sequence counter, in the range - ``[0, SEQUENCE_ID_MAX]``. - node_id: The identifier of this node, in the range ``[0, NODE_ID_MAX]``. - Optional; defaults to ``NODE_ID_DEFAULT``. - epoch_ms: The start of the epoch as Unix milliseconds. Optional; - defaults to the original Twitter epoch (2010-11-04 01:42:54.657 - UTC). - - Returns: - The Snowflake identifier as a positive 63-bit integer, or ``None`` if - ``node_id`` is outside ``[0, NODE_ID_MAX]``, ``sequence_id`` is outside - ``[0, SEQUENCE_ID_MAX]``, or the elapsed time no longer fits in the - timestamp field (roughly 69 years after ``epoch_ms``). In each of those - cases an explanatory message is printed to stdout first. - """ - # TODO: реализуйте функцию - return 0 + if not (0 <= node_id < NODE_ID_MAX): + print(f"node_id must be in [0, {NODE_ID_MAX}], but it is {node_id}") + return None + if not (0 <= sequence_id < SEQUENCE_ID_MAX): + print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], but it is {sequence_id}") + return None + + epoch_ms = time.time() - EPOCH_MS_DEFAULT + if not (0 <= epoch_ms < TIMESTAMP_MS_MAX): + print("overflow") + return None + + return ( + (epoch_ms << NODE_ID_MAX << SEQUENCE_ID_MAX) | (node_id << SEQUENCE_ID_MAX) + ) | sequence_id From 749cadeff3336ca1eb355c222df93f6cfe7eea22 Mon Sep 17 00:00:00 2001 From: Elena Krivchanskaya Date: Thu, 24 Sep 2026 00:55:47 +0300 Subject: [PATCH 3/7] Update snowflake.py update --- src/part1/snowflake.py | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py index 858d4b0e..1668befb 100644 --- a/src/part1/snowflake.py +++ b/src/part1/snowflake.py @@ -28,7 +28,7 @@ def read_current_millis(epoch_ms: int) -> int: - return time.time() - epoch_ms - EPOCH_MS_DEFAULT + return int(time.time()) * 1000 - epoch_ms - EPOCH_MS_DEFAULT def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int: @@ -58,7 +58,7 @@ def generate_snowflake_id( print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], but it is {sequence_id}") return None - epoch_ms = time.time() - EPOCH_MS_DEFAULT + epoch_ms = int(time.time()) * 1000 - EPOCH_MS_DEFAULT if not (0 <= epoch_ms < TIMESTAMP_MS_MAX): print("overflow") return None From 97d390d85a809f317a1b7341d56b2b21be9ecef5 Mon Sep 17 00:00:00 2001 From: Elena Krivchanskaya Date: Mon, 28 Sep 2026 23:04:45 +0300 Subject: [PATCH 4/7] Update utils.py Second task utils --- src/part2/utils.py | 27 ++++----------------------- 1 file changed, 4 insertions(+), 23 deletions(-) diff --git a/src/part2/utils.py b/src/part2/utils.py index ec0348d3..1efcd42a 100644 --- a/src/part2/utils.py +++ b/src/part2/utils.py @@ -1,29 +1,10 @@ -"""Standalone helpers shared by the hw4 storage and CRUD modules. - -For now this is limited to money handling: :func:`normalize_price` rounds a -raw :class:`~decimal.Decimal` amount to the fixed number of fractional -digits (:data:`PRICE_PRECISION`) that every stored price uses, keeping -currency values free of binary floating-point error. -""" - -from decimal import ROUND_HALF_UP, Decimal # noqa: F401 +from decimal import ROUND_HALF_UP, Decimal from typing import Final -# TODO: задайте число знаков после запятой и шаг квантования -PRICE_PRECISION: Final[int] = 0 -PRICE_STEP: Final = Decimal(0) +PRICE_PRECISION: Final[int] = 2 +PRICE_STEP: Final = Decimal(1).scaleb(-PRICE_PRECISION) def normalize_price(price: Decimal) -> Decimal: - """Round a price to the precision every stored record uses. - - Args: - price: The raw price amount. - - Returns: - ``price`` quantised to :data:`PRICE_PRECISION` fractional digits, - with halves rounded up. - """ - # TODO: реализуйте функцию - return Decimal(0) + return price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP) From 8dc93d5e1f6723be3b070205d51ef2e1f202dd24 Mon Sep 17 00:00:00 2001 From: Elena Krivchanskaya Date: Mon, 28 Sep 2026 23:04:58 +0300 Subject: [PATCH 5/7] Update crud.py second task crud --- src/part2/crud.py | 128 +++++++++++++--------------------------------- 1 file changed, 36 insertions(+), 92 deletions(-) diff --git a/src/part2/crud.py b/src/part2/crud.py index d026cbcb..d221216a 100644 --- a/src/part2/crud.py +++ b/src/part2/crud.py @@ -1,79 +1,39 @@ -"""Create/read/update/delete operations over the in-memory product store. - -Every operation takes the store -- a list of -:data:`~src.part2.storage.Product` tuples -- as its first argument and -works on it in place. The failure path never raises: the operation prints -an explanatory message to stdout and returns ``None``. - -The identifier of a new product is derived from the store itself -(:func:`generate_product_id`): one past the greatest identifier in use, or -:data:`~src.part2.storage.PRODUCT_ID_MIN` when the store is empty. -Product names are kept unique -- :func:`create_product` refuses a name that -is already taken. -""" - from decimal import Decimal -from .storage import ( # noqa: F401 +from .storage import ( NAME_INDEX, PRODUCT_ID_INDEX, PRODUCT_ID_MIN, Product, ) -from .utils import normalize_price # noqa: F401 +from .utils import normalize_price def generate_product_id(storage: list[Product]) -> int: - """Choose the identifier for the next product added to ``storage``. - - Args: - storage: The product store to inspect. - - Returns: - One past the greatest identifier currently held in ``storage``, or - :data:`~src.part2.storage.PRODUCT_ID_MIN` when ``storage`` is - empty. - """ - # TODO: реализуйте функцию - return 0 + if len(storage) == 0: + return PRODUCT_ID_MIN + res = (max(storage, key=lambda prod: prod[PRODUCT_ID_INDEX]))[PRODUCT_ID_INDEX] + 1 + return res def create_product( storage: list[Product], fields: tuple[str, Decimal, int] ) -> int | None: - """Append a new product to ``storage`` and return its new identifier. - - Args: - storage: The product store to append to; modified in place on - success. - fields: A ``(name, price, quantity)`` tuple describing the product. - ``price`` is a :class:`~decimal.Decimal` amount and is rounded - to the stored money precision before it is saved. - - Returns: - The identifier generated for the new product, or ``None`` when a - product with the same name already exists. In the ``None`` case - ``storage`` is left unchanged and a message naming the clashing - name is printed. - """ - # TODO: реализуйте функцию - return 0 + if any(prod[NAME_INDEX] == fields[0] for prod in storage): + print(f"product name {fields[0]} is already taken") + return None + cur_id = generate_product_id(storage) + result: Product = (cur_id, fields[0], normalize_price(fields[1]), fields[2]) + storage.append(result) + return cur_id def read_product(storage: list[Product], product_id: int) -> Product | None: - """Return the product stored under ``product_id``. - - Args: - storage: The product store to search. - product_id: The identifier to look up. - - Returns: - The matching ``(product_id, name, price, quantity)`` record, or - ``None`` when no product carries that identifier (a message is - printed in that case). - """ - # TODO: реализуйте функцию - return (0, "", Decimal(0), 0) + for prod in storage: + if prod[PRODUCT_ID_INDEX] == product_id: + return prod + print(f"no product with id {product_id}") + return None def update_product( @@ -81,40 +41,24 @@ def update_product( product_id: int, fields: tuple[str, Decimal, int], ) -> Product | None: - """Overwrite the fields of the product stored under ``product_id``. - - The identifier itself is preserved; only ``name``, ``price`` and - ``quantity`` are replaced. - - Args: - storage: The product store to modify; the matching record is - replaced in place on success. - product_id: The identifier of the product to change. - fields: A ``(name, price, quantity)`` tuple with the new values. - ``price`` is a :class:`~decimal.Decimal` amount and is rounded - to the stored money precision before it is saved. - - Returns: - The updated ``(product_id, name, price, quantity)`` record, or - ``None`` when no product carries that identifier (``storage`` is - left unchanged and a message is printed). - """ - # TODO: реализуйте функцию - return (0, "", Decimal(0), 0) + for ind in range(len(storage)): + if storage[ind][PRODUCT_ID_INDEX] == product_id: + new_product: Product = ( + product_id, + fields[0], + normalize_price(fields[1]), + fields[2], + ) + storage[ind] = new_product + return storage[ind] + print(f"no product with id {product_id}") + return None def delete_product(storage: list[Product], product_id: int) -> int | None: - """Remove the product stored under ``product_id`` from ``storage``. - - Args: - storage: The product store to remove from; modified in place on - success. - product_id: The identifier of the product to remove. - - Returns: - ``product_id`` when a product was removed, or ``None`` when no - product carried that identifier (``storage`` is left unchanged and - a message is printed). - """ - # TODO: реализуйте функцию - return 0 + for ind in range(len(storage)): + if storage[ind][PRODUCT_ID_INDEX] == product_id: + del storage[ind] + return product_id + print(f"no product with id {product_id}") + return None From f9153b3b59dec0758fba40c0d4d6a229b0a13d88 Mon Sep 17 00:00:00 2001 From: Elena Krivchanskaya Date: Mon, 28 Sep 2026 23:05:21 +0300 Subject: [PATCH 6/7] Update storage.py second task storage --- src/part2/storage.py | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/src/part2/storage.py b/src/part2/storage.py index b63d5fc7..35821c5f 100644 --- a/src/part2/storage.py +++ b/src/part2/storage.py @@ -26,9 +26,9 @@ # TODO: задайте позиции полей внутри кортежа Product PRODUCT_ID_INDEX: Final = 0 -NAME_INDEX: Final = 0 -PRICE_INDEX: Final = 0 -QUANTITY_INDEX: Final = 0 +NAME_INDEX: Final = 1 +PRICE_INDEX: Final = 2 +QUANTITY_INDEX: Final = 3 # TODO: задайте идентификатор первого товара в пустом хранилище -PRODUCT_ID_MIN: Final[int] = 0 +PRODUCT_ID_MIN: Final[int] = 1 From fddb8de39f1fe2675b932cafc1e956a6c92f2fe0 Mon Sep 17 00:00:00 2001 From: Elena Krivchanskaya Date: Mon, 28 Sep 2026 23:05:34 +0300 Subject: [PATCH 7/7] Update cart.py second task cart --- src/part2/cart.py | 133 +++++++++++++++++++++++++--------------------- 1 file changed, 72 insertions(+), 61 deletions(-) diff --git a/src/part2/cart.py b/src/part2/cart.py index 063f9aea..ca4859e1 100644 --- a/src/part2/cart.py +++ b/src/part2/cart.py @@ -1,18 +1,7 @@ -"""Shopping-cart operations layered on top of the product store. - -The cart is a plain list of tuples, one :data:`CartLine` -- -``(product_id, quantity)`` -- per distinct product. Moving units between the -store and the cart keeps the two sides in balance: :func:`add_to_cart` takes -units out of stock, :func:`remove_from_cart` puts them back. - -Like the CRUD layer, the failure path never raises -- the operation prints -an explanatory message to stdout and returns ``None``. -""" - from typing import Final -from .crud import read_product, update_product # noqa: F401 -from .storage import ( # noqa: F401 +from .crud import read_product, update_product +from .storage import ( NAME_INDEX, PRICE_INDEX, QUANTITY_INDEX, @@ -22,9 +11,34 @@ type CartLine = tuple[int, int] -# TODO: задайте позиции полей внутри кортежа CartLine + LINE_PRODUCT_ID_INDEX: Final = 0 -LINE_QUANTITY_INDEX: Final = 0 +LINE_QUANTITY_INDEX: Final = 1 + + +def find_cart_line(cart: list[CartLine], product_id: int) -> CartLine | None: + for c_prod in cart: + if c_prod[LINE_PRODUCT_ID_INDEX] == product_id: + return c_prod + print(f"no product with id {product_id} in the cart") + return None + + +def change_cart_quantity( + cart: list[CartLine], + product_id: int, + quantity: int, +) -> int | None: + for ind in range(len(cart)): + if cart[ind][LINE_PRODUCT_ID_INDEX] == product_id: + new_c_prod: CartLine = ( + product_id, + cart[ind][LINE_QUANTITY_INDEX] - quantity, + ) + cart[ind] = new_c_prod + return ind + print(f"no product with id {product_id} in cart") + return None def add_to_cart( @@ -33,28 +47,25 @@ def add_to_cart( product_id: int, quantity: int, ) -> CartLine | None: - """Move ``quantity`` units of ``product_id`` from the store into ``cart``. - - The product is looked up in ``storage``. If it is missing, a message is - printed (by :func:`~src.part2.crud.read_product`) and nothing - changes. If the store holds fewer units than requested, an explanatory - message is printed and nothing changes. Otherwise the store record is - decremented by ``quantity`` and the cart line for ``product_id`` gains - ``quantity`` units -- a new line is created when the cart had none. - - Args: - storage: The product store to draw stock from; modified in place on - success. - cart: The cart to add the units to; modified in place on success. - product_id: The identifier of the product to add. - quantity: Number of units to move into the cart. - - Returns: - The cart line for ``product_id`` after the addition, or ``None`` - when the product is unknown or the store cannot cover the request. - """ - # TODO: реализуйте функцию - return (0, 0) + prod = read_product(storage, product_id) + if prod is None: + return None + if prod[QUANTITY_INDEX] < quantity: + print( + f"not enough stock for product {product_id}: {prod[QUANTITY_INDEX]} available, {quantity} requested" + ) + return None + update_product( + storage, + product_id, + (prod[NAME_INDEX], prod[PRICE_INDEX], prod[QUANTITY_INDEX] - quantity), + ) + for ind in range(len(cart)): + if cart[ind][LINE_PRODUCT_ID_INDEX] == product_id: + cart[ind] = (product_id, cart[ind][LINE_QUANTITY_INDEX] + quantity) + return cart[ind] + cart.append((product_id, quantity)) + return cart[-1] def remove_from_cart( @@ -63,27 +74,27 @@ def remove_from_cart( product_id: int, quantity: int, ) -> CartLine | None: - """Move ``quantity`` units of ``product_id`` from ``cart`` back to the store. - - The cart line for ``product_id`` is looked up. If there is none, a - message is printed and nothing changes. If the line holds fewer units - than requested, an explanatory message is printed and nothing changes. - Otherwise the cart line loses ``quantity`` units -- the line is dropped - when it reaches zero -- and the store record gains ``quantity`` units - back. - - Args: - storage: The product store to return stock to; modified in place on - success. - cart: The cart to take the units from; modified in place on - success. - product_id: The identifier of the product to remove. - quantity: Number of units to move back into the store. - - Returns: - The cart line for ``product_id`` after the removal (a quantity of - zero means the line was dropped), or ``None`` when the cart has no - line for the product or holds too few units. - """ - # TODO: реализуйте функцию - return (0, 0) + c_prod = find_cart_line(cart, product_id) + if c_prod is None: + return None + if c_prod[LINE_QUANTITY_INDEX] < quantity: + print( + f"cart holds only {c_prod[LINE_QUANTITY_INDEX]} unit(s) of product {product_id}, cannot remove {quantity}" + ) + return None + prod = read_product(storage, product_id) + if prod is None: + return None + update_product( + storage, + product_id, + (prod[NAME_INDEX], prod[PRICE_INDEX], prod[QUANTITY_INDEX] + quantity), + ) + ind = change_cart_quantity(cart, product_id, quantity) + if ind is None: + return None + if cart[ind][LINE_QUANTITY_INDEX] == 0: + res = cart[ind] + del cart[ind] + return res + return cart[ind]