From e16319f4cdd0e6a02f0a02943773b1d61b34239d Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 25 Sep 2026 20:49:03 +0300
Subject: [PATCH 01/15] task

---
 src/part1/constants.py | 19 +++++++++++--------
 src/part1/snowflake.py | 34 ++++++++++++++++++++++++++--------
 2 files changed, 37 insertions(+), 16 deletions(-)

diff --git a/src/part1/constants.py b/src/part1/constants.py
index 9abfbba2..bff179aa 100644
--- a/src/part1/constants.py
+++ b/src/part1/constants.py
@@ -19,20 +19,23 @@
 # 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] = (1 << TIMESTAMP_BITS) - 1
+NODE_ID_MAX: Final[int] = (1 << NODE_ID_BITS) - 1
+SEQUENCE_ID_MAX: Final[int] = (1 << SEQUENCE_ID_BITS) - 1
 
 # Здесь можно добавить собственные вспомогательные константы
 # (например, сдвиги полей при сборке идентификатора).
+SEQUENCE_ID_SHIFT: Final[int] = 0  # справа(младшие разряды)
+NODE_ID_SHIFT: Final[int] = SEQUENCE_ID_BITS
+TIMESTAMP_SHIFT: Final[int] = SEQUENCE_ID_BITS + NODE_ID_BITS
diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py
index d3abf050..0a09b53b 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -13,14 +13,17 @@
 :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_DEFAULT,
     NODE_ID_MAX,
+    NODE_ID_SHIFT,
+    SEQUENCE_ID_BITS,
     SEQUENCE_ID_MAX,
     TIMESTAMP_MS_MAX,
+    TIMESTAMP_SHIFT,
 )
 
 
@@ -34,8 +37,7 @@ def read_current_millis(epoch_ms: int) -> int:
         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 int(time.time() * 1000) - epoch_ms
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
@@ -51,7 +53,8 @@ def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) ->
         generated.
     """
     # TODO: реализуйте функцию
-    return 0
+    time_res = snowflake_id >> TIMESTAMP_SHIFT
+    return time_res + epoch_ms
 
 
 def decode_node_id(snowflake_id: int) -> int:
@@ -65,7 +68,8 @@ def decode_node_id(snowflake_id: int) -> int:
         ``[0, NODE_ID_MAX]``.
     """
     # TODO: реализуйте функцию
-    return 0
+    node_id = (snowflake_id >> SEQUENCE_ID_BITS) & NODE_ID_MAX
+    return node_id
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
@@ -79,7 +83,8 @@ def decode_sequence_id(snowflake_id: int) -> int:
         the range ``[0, SEQUENCE_ID_MAX]``.
     """
     # TODO: реализуйте функцию
-    return 0
+    sequence_id = snowflake_id & SEQUENCE_ID_MAX
+    return sequence_id
 
 
 def generate_snowflake_id(
@@ -111,4 +116,17 @@ def generate_snowflake_id(
         cases an explanatory message is printed to stdout first.
     """
     # TODO: реализуйте функцию
-    return 0
+    if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
+        print(f"sequence_id must be >= 0 and <= {SEQUENCE_ID_MAX}")
+        return None
+    if not (0 <= node_id <= NODE_ID_MAX):
+        print(f"node_id must be >= 0 and <= {NODE_ID_MAX}")
+        return None
+    timestamp = read_current_millis(epoch_ms)
+    if not (0 <= timestamp <= TIMESTAMP_MS_MAX):
+        print(f"timestamp must be >= 0 and <= {TIMESTAMP_MS_MAX}")
+        return None
+    node_res = node_id << NODE_ID_SHIFT
+    timestamp_res = timestamp << TIMESTAMP_SHIFT
+    result = timestamp_res | node_res | sequence_id
+    return result

From 4580922e3ecf81ee40f574a12e5f5e8132a6ae50 Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 25 Sep 2026 21:26:35 +0300
Subject: [PATCH 02/15] Solve task 1

---
 src/part1/snowflake.py | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py
index 0a09b53b..4d08ab45 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -15,7 +15,7 @@
 
 import time
 
-from .constants import (
+from constants import (
     EPOCH_MS_DEFAULT,
     NODE_ID_DEFAULT,
     NODE_ID_MAX,
@@ -117,16 +117,17 @@ def generate_snowflake_id(
     """
     # TODO: реализуйте функцию
     if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
-        print(f"sequence_id must be >= 0 and <= {SEQUENCE_ID_MAX}")
+        print(f"sequence_id must be in >= 0 and <= {SEQUENCE_ID_MAX}")
         return None
     if not (0 <= node_id <= NODE_ID_MAX):
-        print(f"node_id must be >= 0 and <= {NODE_ID_MAX}")
+        print(f"node_id must be in >= 0 and <= {NODE_ID_MAX}")
         return None
     timestamp = read_current_millis(epoch_ms)
     if not (0 <= timestamp <= TIMESTAMP_MS_MAX):
-        print(f"timestamp must be >= 0 and <= {TIMESTAMP_MS_MAX}")
+        print(f"overflows")
         return None
     node_res = node_id << NODE_ID_SHIFT
     timestamp_res = timestamp << TIMESTAMP_SHIFT
     result = timestamp_res | node_res | sequence_id
     return result
+print(generate_snowflake_id(0, -1))

From 3bd6743461216cccfcc5649ae03d3d9a6dcda941 Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 25 Sep 2026 21:30:46 +0300
Subject: [PATCH 03/15] Solve task 1

---
 src/part1/snowflake.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py
index 4d08ab45..b67739a5 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -15,7 +15,7 @@
 
 import time
 
-from constants import (
+from .constants import (
     EPOCH_MS_DEFAULT,
     NODE_ID_DEFAULT,
     NODE_ID_MAX,
@@ -116,12 +116,12 @@ def generate_snowflake_id(
         cases an explanatory message is printed to stdout first.
     """
     # TODO: реализуйте функцию
-    if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
-        print(f"sequence_id must be in >= 0 and <= {SEQUENCE_ID_MAX}")
-        return None
     if not (0 <= node_id <= NODE_ID_MAX):
         print(f"node_id must be in >= 0 and <= {NODE_ID_MAX}")
         return None
+    if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
+        print(f"sequence_id must be in >= 0 and <= {SEQUENCE_ID_MAX}")
+        return None
     timestamp = read_current_millis(epoch_ms)
     if not (0 <= timestamp <= TIMESTAMP_MS_MAX):
         print(f"overflows")

From 894a8049e42606a5c30b037c246815e17d162803 Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 25 Sep 2026 21:35:14 +0300
Subject: [PATCH 04/15] Solve task 1

---
 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 b67739a5..12da3cae 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -117,10 +117,10 @@ def generate_snowflake_id(
     """
     # TODO: реализуйте функцию
     if not (0 <= node_id <= NODE_ID_MAX):
-        print(f"node_id must be in >= 0 and <= {NODE_ID_MAX}")
+        print(f"node_id must be [0, {NODE_ID_MAX}]")
         return None
     if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
-        print(f"sequence_id must be in >= 0 and <= {SEQUENCE_ID_MAX}")
+        print(f"sequence_id must be [0, {SEQUENCE_ID_MAX}")
         return None
     timestamp = read_current_millis(epoch_ms)
     if not (0 <= timestamp <= TIMESTAMP_MS_MAX):

From da1a28409c4f734333ad327eebcacdfac2e98748 Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 25 Sep 2026 21:39:04 +0300
Subject: [PATCH 05/15] Solve task 1

---
 src/part1/snowflake.py | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py
index 12da3cae..4a3d902e 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -117,10 +117,10 @@ def generate_snowflake_id(
     """
     # TODO: реализуйте функцию
     if not (0 <= node_id <= NODE_ID_MAX):
-        print(f"node_id must be [0, {NODE_ID_MAX}]")
+        print(f"node_id must be in [0, {NODE_ID_MAX}]")
         return None
     if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
-        print(f"sequence_id must be [0, {SEQUENCE_ID_MAX}")
+        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}")
         return None
     timestamp = read_current_millis(epoch_ms)
     if not (0 <= timestamp <= TIMESTAMP_MS_MAX):
@@ -130,4 +130,3 @@ def generate_snowflake_id(
     timestamp_res = timestamp << TIMESTAMP_SHIFT
     result = timestamp_res | node_res | sequence_id
     return result
-print(generate_snowflake_id(0, -1))

From 9eb51cfdb614290d55135d34299fba51d39f3b95 Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 25 Sep 2026 21:40:01 +0300
Subject: [PATCH 06/15] Solve task 1

---
 src/part1/snowflake.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py
index 4a3d902e..35733c24 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -120,7 +120,7 @@ def generate_snowflake_id(
         print(f"node_id must be in [0, {NODE_ID_MAX}]")
         return None
     if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
-        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}")
+        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}]")
         return None
     timestamp = read_current_millis(epoch_ms)
     if not (0 <= timestamp <= TIMESTAMP_MS_MAX):

From ff147586fff55520d851141e1791d4e396b799b0 Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 25 Sep 2026 21:46:08 +0300
Subject: [PATCH 07/15] Solve task 1

---
 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 35733c24..d1fbb88f 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -117,10 +117,10 @@ def generate_snowflake_id(
     """
     # TODO: реализуйте функцию
     if not (0 <= node_id <= NODE_ID_MAX):
-        print(f"node_id must be in [0, {NODE_ID_MAX}]")
+        print(f"node_id must be in [0, {NODE_ID_MAX}], but you wrote {node_id}")
         return None
     if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
-        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}]")
+        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], but you wrote {sequence_id}")
         return None
     timestamp = read_current_millis(epoch_ms)
     if not (0 <= timestamp <= TIMESTAMP_MS_MAX):

From c6aa5e575b9cbc44f98a4d638573b412c0fe2e40 Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 25 Sep 2026 21:47:05 +0300
Subject: [PATCH 08/15] Solve task 1

---
 src/part1/snowflake.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py
index d1fbb88f..a07bdd77 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -124,7 +124,7 @@ def generate_snowflake_id(
         return None
     timestamp = read_current_millis(epoch_ms)
     if not (0 <= timestamp <= TIMESTAMP_MS_MAX):
-        print(f"overflows")
+        print("overflows")
         return None
     node_res = node_id << NODE_ID_SHIFT
     timestamp_res = timestamp << TIMESTAMP_SHIFT

From 4d222137bebea2174b72c84ffa817932a6b971d8 Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 25 Sep 2026 23:11:11 +0300
Subject: [PATCH 09/15] Solve task 1

---
 src/part1/snowflake.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py
index a07bdd77..0777a5ee 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -117,10 +117,14 @@ def generate_snowflake_id(
     """
     # TODO: реализуйте функцию
     if not (0 <= node_id <= NODE_ID_MAX):
-        print(f"node_id must be in [0, {NODE_ID_MAX}], but you wrote {node_id}")
+        print(
+            f"node_id must be in [0, {NODE_ID_MAX}], but you wrote {node_id}"
+            )
         return None
     if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
-        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], but you wrote {sequence_id}")
+        print(
+            f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], but you wrote {sequence_id}"
+            )
         return None
     timestamp = read_current_millis(epoch_ms)
     if not (0 <= timestamp <= TIMESTAMP_MS_MAX):

From 18cdca82d44f83e0bfec9252f84e7944e37dd4b2 Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 25 Sep 2026 23:20:51 +0300
Subject: [PATCH 10/15] Solve task 1

---
 src/part1/snowflake.py | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py
index 0777a5ee..56204d22 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -117,14 +117,12 @@ def generate_snowflake_id(
     """
     # TODO: реализуйте функцию
     if not (0 <= node_id <= NODE_ID_MAX):
-        print(
-            f"node_id must be in [0, {NODE_ID_MAX}], but you wrote {node_id}"
-            )
+        print(f"node_id must be in [0, {NODE_ID_MAX}], but you wrote {node_id}")
         return None
     if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
         print(
             f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], but you wrote {sequence_id}"
-            )
+        )
         return None
     timestamp = read_current_millis(epoch_ms)
     if not (0 <= timestamp <= TIMESTAMP_MS_MAX):

From bfaa64b7c00aa42c2b8d6c500631f19b95ed92ea Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 2 Oct 2026 20:05:33 +0300
Subject: [PATCH 11/15] Solve task 2

---
 src/part2/cart.py    | 47 ++++++++++++++++++++++++++++++++++++++++----
 src/part2/crud.py    | 41 ++++++++++++++++++++++++++++++++------
 src/part2/storage.py |  8 ++++----
 src/part2/utils.py   |  6 +++---
 4 files changed, 85 insertions(+), 17 deletions(-)

diff --git a/src/part2/cart.py b/src/part2/cart.py
index 063f9aea..2ec984eb 100644
--- a/src/part2/cart.py
+++ b/src/part2/cart.py
@@ -24,8 +24,13 @@
 
 # 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 line in cart:
+        if line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return line
+    return None
 
 def add_to_cart(
     storage: list[Product],
@@ -54,8 +59,21 @@ def add_to_cart(
         when the product is unknown or the store cannot cover the request.
     """
     # TODO: реализуйте функцию
-    return (0, 0)
-
+    product = read_product(storage, product_id)
+    if product:
+        if product[QUANTITY_INDEX] < quantity:
+            print(f"not enough stock for product {product_id}: {product[QUANTITY_INDEX]} available, {quantity} requested")
+            return None
+        product = update_product(storage, product_id, (product[NAME_INDEX], product[PRICE_INDEX], product[QUANTITY_INDEX] - quantity))
+        for line in cart:
+            if line[LINE_PRODUCT_ID_INDEX] == product_id:
+                new_line = (product_id, line[LINE_QUANTITY_INDEX] + quantity)
+                cart[cart.index(line)] = new_line
+                return new_line
+        new_line =(product_id, quantity)
+        cart.append(new_line)
+        return new_line
+    return None
 
 def remove_from_cart(
     storage: list[Product],
@@ -86,4 +104,25 @@ def remove_from_cart(
         line for the product or holds too few units.
     """
     # TODO: реализуйте функцию
-    return (0, 0)
+    line = find_cart_line(cart, product_id)
+    if line is None:
+        print(f"product {product_id} is not in the cart")
+        return None
+    if line[LINE_QUANTITY_INDEX] < quantity:
+        print(f"cart holds only {line[LINE_QUANTITY_INDEX]} unit(s) "
+              f"of product {product_id}, cannot remove {quantity}")
+        return None
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+    update_product(
+    storage,
+    product_id,
+    (product[NAME_INDEX], product[PRICE_INDEX], product[QUANTITY_INDEX] + quantity,),)
+    new_quantity = line[LINE_QUANTITY_INDEX] - quantity
+    if new_quantity == 0:
+        cart.remove(line)
+        return (product_id, 0)
+    new_line = (product_id, new_quantity)
+    cart[cart.index(line)] = new_line
+    return new_line
\ No newline at end of file
diff --git a/src/part2/crud.py b/src/part2/crud.py
index d026cbcb..20da24e9 100644
--- a/src/part2/crud.py
+++ b/src/part2/crud.py
@@ -35,8 +35,12 @@ def generate_product_id(storage: list[Product]) -> int:
         empty.
     """
     # TODO: реализуйте функцию
-    return 0
-
+    if not storage:
+        return PRODUCT_ID_MIN
+    max_id = 0
+    for product in storage:
+        max_id = max(max_id, product[PRODUCT_ID_INDEX])
+    return max_id + 1
 
 def create_product(
     storage: list[Product], fields: tuple[str, Decimal, int]
@@ -57,7 +61,15 @@ def create_product(
         name is printed.
     """
     # TODO: реализуйте функцию
-    return 0
+    name, price, quantity = fields
+    for product in storage:
+        if product[NAME_INDEX] == name:
+            print(f"product name '{name}' is already taken")
+            return None
+    product_id = generate_product_id(storage)
+    normalized_price = normalize_price(price)
+    storage.append((product_id, name, normalized_price, quantity))
+    return product_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -73,7 +85,11 @@ def read_product(storage: list[Product], product_id: int) -> Product | None:
         printed in that case).
     """
     # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            return product
+    print(f"no product with id {product_id}")
+    return None
 
 
 def update_product(
@@ -100,7 +116,15 @@ def update_product(
         left unchanged and a message is printed).
     """
     # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    name, price, quantity = fields
+    price = normalize_price(price)
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            updated_product = (product_id, name, price, quantity)
+            storage[storage.index(product)] = updated_product
+            return updated_product
+    print(f"no product with id {product_id}")
+    return None
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
@@ -117,4 +141,9 @@ def delete_product(storage: list[Product], product_id: int) -> int | None:
         a message is printed).
     """
     # TODO: реализуйте функцию
-    return 0
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            storage.remove(product)
+            return product_id
+    print(f"no product with id {product_id}")
+    return None
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
diff --git a/src/part2/utils.py b/src/part2/utils.py
index ec0348d3..f4cdc43b 100644
--- a/src/part2/utils.py
+++ b/src/part2/utils.py
@@ -11,8 +11,8 @@
 
 
 # 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:
@@ -26,4 +26,4 @@ def normalize_price(price: Decimal) -> Decimal:
         with halves rounded up.
     """
     # TODO: реализуйте функцию
-    return Decimal(0)
+    return price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP)

From fc2b9e38c8f3bb85f758fb9e49695b09f22c0687 Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 2 Oct 2026 21:15:37 +0300
Subject: [PATCH 12/15] Solve task 2

---
 src/part2/cart.py  | 42 +++++++++++++++++++++++++++++++-----------
 src/part2/crud.py  |  5 +++--
 src/part2/utils.py |  2 +-
 3 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/src/part2/cart.py b/src/part2/cart.py
index 2ec984eb..51afb1e5 100644
--- a/src/part2/cart.py
+++ b/src/part2/cart.py
@@ -11,8 +11,8 @@
 
 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,
@@ -26,12 +26,14 @@
 LINE_PRODUCT_ID_INDEX: Final = 0
 LINE_QUANTITY_INDEX: Final = 1
 
+
 def find_cart_line(cart: list[CartLine], product_id: int) -> CartLine | None:
     for line in cart:
         if line[LINE_PRODUCT_ID_INDEX] == product_id:
             return line
     return None
 
+
 def add_to_cart(
     storage: list[Product],
     cart: list[CartLine],
@@ -62,19 +64,30 @@ def add_to_cart(
     product = read_product(storage, product_id)
     if product:
         if product[QUANTITY_INDEX] < quantity:
-            print(f"not enough stock for product {product_id}: {product[QUANTITY_INDEX]} available, {quantity} requested")
+            print(
+                f"not enough stock for product {product_id}: {product[QUANTITY_INDEX]} available, {quantity} requested"
+            )
             return None
-        product = update_product(storage, product_id, (product[NAME_INDEX], product[PRICE_INDEX], product[QUANTITY_INDEX] - quantity))
+        product = update_product(
+            storage,
+            product_id,
+            (
+                product[NAME_INDEX],
+                product[PRICE_INDEX],
+                product[QUANTITY_INDEX] - quantity,
+            ),
+        )
         for line in cart:
             if line[LINE_PRODUCT_ID_INDEX] == product_id:
                 new_line = (product_id, line[LINE_QUANTITY_INDEX] + quantity)
                 cart[cart.index(line)] = new_line
                 return new_line
-        new_line =(product_id, quantity)
+        new_line = (product_id, quantity)
         cart.append(new_line)
         return new_line
     return None
 
+
 def remove_from_cart(
     storage: list[Product],
     cart: list[CartLine],
@@ -109,20 +122,27 @@ def remove_from_cart(
         print(f"product {product_id} is not in the cart")
         return None
     if line[LINE_QUANTITY_INDEX] < quantity:
-        print(f"cart holds only {line[LINE_QUANTITY_INDEX]} unit(s) "
-              f"of product {product_id}, cannot remove {quantity}")
+        print(
+            f"cart holds only {line[LINE_QUANTITY_INDEX]} unit(s) "
+            f"of product {product_id}, cannot remove {quantity}"
+        )
         return None
     product = read_product(storage, product_id)
     if product is None:
         return None
     update_product(
-    storage,
-    product_id,
-    (product[NAME_INDEX], product[PRICE_INDEX], product[QUANTITY_INDEX] + quantity,),)
+        storage,
+        product_id,
+        (
+            product[NAME_INDEX],
+            product[PRICE_INDEX],
+            product[QUANTITY_INDEX] + quantity,
+        ),
+    )
     new_quantity = line[LINE_QUANTITY_INDEX] - quantity
     if new_quantity == 0:
         cart.remove(line)
         return (product_id, 0)
     new_line = (product_id, new_quantity)
     cart[cart.index(line)] = new_line
-    return new_line
\ No newline at end of file
+    return new_line
diff --git a/src/part2/crud.py b/src/part2/crud.py
index 20da24e9..ee88d7e0 100644
--- a/src/part2/crud.py
+++ b/src/part2/crud.py
@@ -14,13 +14,13 @@
 
 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:
@@ -42,6 +42,7 @@ def generate_product_id(storage: list[Product]) -> int:
         max_id = max(max_id, product[PRODUCT_ID_INDEX])
     return max_id + 1
 
+
 def create_product(
     storage: list[Product], fields: tuple[str, Decimal, int]
 ) -> int | None:
diff --git a/src/part2/utils.py b/src/part2/utils.py
index f4cdc43b..26a20798 100644
--- a/src/part2/utils.py
+++ b/src/part2/utils.py
@@ -6,7 +6,7 @@
 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
 
 

From 0ac733b16d9d1d00d7f805e91aca41434935cb1e Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 2 Oct 2026 22:57:14 +0300
Subject: [PATCH 13/15] Solve task 2

---
 src/part2/cart.py    | 19 +++++++++++++------
 src/part2/crud.py    | 25 +++++++++++++++++++++----
 src/part2/storage.py |  8 ++++----
 3 files changed, 38 insertions(+), 14 deletions(-)

diff --git a/src/part2/cart.py b/src/part2/cart.py
index 51afb1e5..adb30264 100644
--- a/src/part2/cart.py
+++ b/src/part2/cart.py
@@ -23,8 +23,15 @@
 type CartLine = tuple[int, int]
 
 # TODO: задайте позиции полей внутри кортежа CartLine
-LINE_PRODUCT_ID_INDEX: Final = 0
-LINE_QUANTITY_INDEX: Final = 1
+LINE_PRODUCT_ID_INDEX: Final = 1
+LINE_QUANTITY_INDEX: Final = 0
+
+
+def make_cart(product_id: int, quantity: int) -> CartLine:  # переставлять
+    fields = [None] * 2
+    fields[LINE_PRODUCT_ID_INDEX] = product_id
+    fields[LINE_QUANTITY_INDEX] = quantity
+    return tuple(fields)
 
 
 def find_cart_line(cart: list[CartLine], product_id: int) -> CartLine | None:
@@ -79,10 +86,10 @@ def add_to_cart(
         )
         for line in cart:
             if line[LINE_PRODUCT_ID_INDEX] == product_id:
-                new_line = (product_id, line[LINE_QUANTITY_INDEX] + quantity)
+                new_line = make_cart(product_id, line[LINE_QUANTITY_INDEX] + quantity)
                 cart[cart.index(line)] = new_line
                 return new_line
-        new_line = (product_id, quantity)
+        new_line = make_cart(product_id, quantity)
         cart.append(new_line)
         return new_line
     return None
@@ -142,7 +149,7 @@ def remove_from_cart(
     new_quantity = line[LINE_QUANTITY_INDEX] - quantity
     if new_quantity == 0:
         cart.remove(line)
-        return (product_id, 0)
-    new_line = (product_id, new_quantity)
+        return make_cart(product_id, 0)
+    new_line = make_cart(product_id, new_quantity)
     cart[cart.index(line)] = new_line
     return new_line
diff --git a/src/part2/crud.py b/src/part2/crud.py
index ee88d7e0..3a8ebaf4 100644
--- a/src/part2/crud.py
+++ b/src/part2/crud.py
@@ -16,13 +16,29 @@
 
 from .storage import (
     NAME_INDEX,
+    PRICE_INDEX,
     PRODUCT_ID_INDEX,
     PRODUCT_ID_MIN,
+    QUANTITY_INDEX,
     Product,
 )
 from .utils import normalize_price
 
 
+def make(  # чтобы можно было переставлять
+    product_id: int,
+    name: str,
+    price: Decimal,
+    quantity: int,
+) -> Product:
+    fields = [None] * 4
+    fields[PRODUCT_ID_INDEX] = product_id
+    fields[NAME_INDEX] = name
+    fields[PRICE_INDEX] = price
+    fields[QUANTITY_INDEX] = quantity
+    return tuple(fields)
+
+
 def generate_product_id(storage: list[Product]) -> int:
     """Choose the identifier for the next product added to ``storage``.
 
@@ -69,7 +85,7 @@ def create_product(
             return None
     product_id = generate_product_id(storage)
     normalized_price = normalize_price(price)
-    storage.append((product_id, name, normalized_price, quantity))
+    storage.append(make(product_id, name, normalized_price, quantity))
     return product_id
 
 
@@ -119,10 +135,11 @@ def update_product(
     # TODO: реализуйте функцию
     name, price, quantity = fields
     price = normalize_price(price)
-    for product in storage:
+    for i in range(len(storage)):
+        product = storage[i]
         if product[PRODUCT_ID_INDEX] == product_id:
-            updated_product = (product_id, name, price, quantity)
-            storage[storage.index(product)] = updated_product
+            updated_product = make(product_id, name, price, quantity)
+            storage[i] = updated_product
             return updated_product
     print(f"no product with id {product_id}")
     return None
diff --git a/src/part2/storage.py b/src/part2/storage.py
index 35821c5f..23bd1b82 100644
--- a/src/part2/storage.py
+++ b/src/part2/storage.py
@@ -25,10 +25,10 @@
 type Product = tuple[int, str, Decimal, int]
 
 # TODO: задайте позиции полей внутри кортежа Product
-PRODUCT_ID_INDEX: Final = 0
-NAME_INDEX: Final = 1
-PRICE_INDEX: Final = 2
-QUANTITY_INDEX: Final = 3
+PRODUCT_ID_INDEX: Final = 3
+NAME_INDEX: Final = 2
+PRICE_INDEX: Final = 1
+QUANTITY_INDEX: Final = 0
 
 # TODO: задайте идентификатор первого товара в пустом хранилище
 PRODUCT_ID_MIN: Final[int] = 1

From f2e1b1fb62d6c969b79ef76efd5aa883991fe7cf Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 2 Oct 2026 23:01:13 +0300
Subject: [PATCH 14/15] Solve task 2

---
 src/part2/cart.py    | 4 ++--
 src/part2/storage.py | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/part2/cart.py b/src/part2/cart.py
index adb30264..35d4f96c 100644
--- a/src/part2/cart.py
+++ b/src/part2/cart.py
@@ -23,8 +23,8 @@
 type CartLine = tuple[int, int]
 
 # TODO: задайте позиции полей внутри кортежа CartLine
-LINE_PRODUCT_ID_INDEX: Final = 1
-LINE_QUANTITY_INDEX: Final = 0
+LINE_PRODUCT_ID_INDEX: Final = 0
+LINE_QUANTITY_INDEX: Final = 1
 
 
 def make_cart(product_id: int, quantity: int) -> CartLine:  # переставлять
diff --git a/src/part2/storage.py b/src/part2/storage.py
index 23bd1b82..35821c5f 100644
--- a/src/part2/storage.py
+++ b/src/part2/storage.py
@@ -25,10 +25,10 @@
 type Product = tuple[int, str, Decimal, int]
 
 # TODO: задайте позиции полей внутри кортежа Product
-PRODUCT_ID_INDEX: Final = 3
-NAME_INDEX: Final = 2
-PRICE_INDEX: Final = 1
-QUANTITY_INDEX: Final = 0
+PRODUCT_ID_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] = 1

From 8744b22580a38b567d2d9dae0438e0aa056e8e2f Mon Sep 17 00:00:00 2001
From: alpen9 <alyapenskaya@yandex.ru>
Date: Fri, 2 Oct 2026 23:45:47 +0300
Subject: [PATCH 15/15] Solve task 2

---
 src/part2/cart.py | 6 +++---
 src/part2/crud.py | 5 +++--
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/part2/cart.py b/src/part2/cart.py
index 35d4f96c..1db63050 100644
--- a/src/part2/cart.py
+++ b/src/part2/cart.py
@@ -9,7 +9,7 @@
 an explanatory message to stdout and returns ``None``.
 """
 
-from typing import Final
+from typing import Final, cast
 
 from .crud import read_product, update_product
 from .storage import (
@@ -28,10 +28,10 @@
 
 
 def make_cart(product_id: int, quantity: int) -> CartLine:  # переставлять
-    fields = [None] * 2
+    fields: list[int] = [0] * 2
     fields[LINE_PRODUCT_ID_INDEX] = product_id
     fields[LINE_QUANTITY_INDEX] = quantity
-    return tuple(fields)
+    return cast(CartLine, tuple(fields))
 
 
 def find_cart_line(cart: list[CartLine], product_id: int) -> CartLine | None:
diff --git a/src/part2/crud.py b/src/part2/crud.py
index 3a8ebaf4..2472a194 100644
--- a/src/part2/crud.py
+++ b/src/part2/crud.py
@@ -13,6 +13,7 @@
 """
 
 from decimal import Decimal
+from typing import cast
 
 from .storage import (
     NAME_INDEX,
@@ -31,12 +32,12 @@ def make(  # чтобы можно было переставлять
     price: Decimal,
     quantity: int,
 ) -> Product:
-    fields = [None] * 4
+    fields: list[int | str | Decimal] = [0] * 4
     fields[PRODUCT_ID_INDEX] = product_id
     fields[NAME_INDEX] = name
     fields[PRICE_INDEX] = price
     fields[QUANTITY_INDEX] = quantity
-    return tuple(fields)
+    return cast(Product, tuple(fields))
 
 
 def generate_product_id(storage: list[Product]) -> int: