{
"cells": [
{
"cell_type": "code",
"execution_count": 1,
"id": "de014d74-4685-4f16-85fd-f571fd5a91db",
"metadata": {},
"outputs": [],
"source": [
"import threading"
]
},
{
"cell_type": "code",
"execution_count": 2,
"id": "82b2f08c-1a13-4a0f-9546-e5d624dbee5b",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
" 0 RESUME 0\n",
"\n",
" 1 LOAD_NAME 0 (total)\n",
" LOAD_CONST 0 (1)\n",
" BINARY_OP 13 (+=)\n",
" STORE_NAME 0 (total)\n",
" RETURN_CONST 1 (None)\n"
]
}
],
"source": [
"import dis\n",
"dis.dis(\"total += 1\")"
]
},
{
"cell_type": "code",
"execution_count": 3,
"id": "ae617ed8-dd51-4154-ad83-308df527d1f1",
"metadata": {},
"outputs": [],
"source": [
"import threading"
]
},
{
"cell_type": "code",
"execution_count": 4,
"id": "b735264e-f27a-4d27-ba5f-4d6a1f53543e",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"CPU times: user 151 ms, sys: 0 ns, total: 151 ms\n",
"Wall time: 148 ms\n"
]
},
{
"data": {
"text/plain": [
"2000000"
]
},
"execution_count": 4,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"%%time\n",
"# 141 ms (no locks)\n",
"# 340 ms (fine-grained locking)\n",
"# 122 ms (coarse-grained locking)\n",
"\n",
"lock = threading.Lock() # this protects total\n",
"total = 0\n",
"\n",
"def task(count):\n",
" global total\n",
" lock.acquire()\n",
" for i in range(count):\n",
" total += 1\n",
" lock.release()\n",
"\n",
"t1 = threading.Thread(target=task, args=[1_000_000])\n",
"t1.start()\n",
"t2 = threading.Thread(target=task, args=[1_000_000])\n",
"t2.start()\n",
"\n",
"t1.join()\n",
"t2.join()\n",
"\n",
"total"
]
},
{
"cell_type": "code",
"execution_count": 5,
"id": "7cf83d46-b7db-4ab6-b0bb-4b35fecba5b2",
"metadata": {},
"outputs": [],
"source": [
"bank_accounts = {\"x\": 25, \"y\": 100, \"z\": 200} # in dollars\n",
"lock = threading.Lock() # protects bank_accounts\n",
"\n",
"def transfer(src, dst, amount):\n",
" with lock: # automatically acquire now, automatically release after the with\n",
" success = False\n",
" if bank_accounts[src] >= amount:\n",
" bank_accounts[src] -= amount\n",
" bank_accounts[dst] += amount\n",
" success = True\n",
" print(\"transferred\" if success else \"denied\")\n",
" print(\"is it locked inside the with?\", lock.locked())\n",
" print(\"is it locked after the with?\", lock.locked())"
]
},
{
"cell_type": "code",
"execution_count": 6,
"id": "c9f19a3d-172f-4103-b631-11b42a8dc94c",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"transferred\n",
"is it locked inside the with? True\n",
"is it locked after the with? False\n"
]
},
{
"data": {
"text/plain": [
"{'x': 5, 'y': 120, 'z': 200}"
]
},
"execution_count": 6,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"transfer(\"x\", \"y\", 20)\n",
"bank_accounts"
]
},
{
"cell_type": "code",
"execution_count": 7,
"id": "bdd94c73-dd01-4b9e-aecc-70faff00685d",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"denied\n",
"is it locked inside the with? True\n",
"is it locked after the with? False\n"
]
},
{
"data": {
"text/plain": [
"{'x': 5, 'y': 120, 'z': 200}"
]
},
"execution_count": 7,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"transfer(\"x\", \"z\", 10)\n",
"bank_accounts"
]
},
{
"cell_type": "code",
"execution_count": 8,
"id": "41f9d7d2-86f8-433c-bf56-724a7f445753",
"metadata": {},
"outputs": [
{
"ename": "KeyError",
"evalue": "'w'",
"output_type": "error",
"traceback": [
"\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
"\u001b[0;31mKeyError\u001b[0m Traceback (most recent call last)",
"Cell \u001b[0;32mIn[8], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mtransfer\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;124;43m\"\u001b[39;49m\u001b[38;5;124;43mw\u001b[39;49m\u001b[38;5;124;43m\"\u001b[39;49m\u001b[43m,\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;124;43m\"\u001b[39;49m\u001b[38;5;124;43mz\u001b[39;49m\u001b[38;5;124;43m\"\u001b[39;49m\u001b[43m,\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;241;43m10\u001b[39;49m\u001b[43m)\u001b[49m \u001b[38;5;66;03m# there is no \"w\" bank account\u001b[39;00m\n\u001b[1;32m 2\u001b[0m bank_accounts\n",
"Cell \u001b[0;32mIn[5], line 7\u001b[0m, in \u001b[0;36mtransfer\u001b[0;34m(src, dst, amount)\u001b[0m\n\u001b[1;32m 5\u001b[0m \u001b[38;5;28;01mwith\u001b[39;00m lock: \u001b[38;5;66;03m# automatically acquire now, automatically release after the with\u001b[39;00m\n\u001b[1;32m 6\u001b[0m success \u001b[38;5;241m=\u001b[39m \u001b[38;5;28;01mFalse\u001b[39;00m\n\u001b[0;32m----> 7\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m \u001b[43mbank_accounts\u001b[49m\u001b[43m[\u001b[49m\u001b[43msrc\u001b[49m\u001b[43m]\u001b[49m \u001b[38;5;241m>\u001b[39m\u001b[38;5;241m=\u001b[39m amount:\n\u001b[1;32m 8\u001b[0m bank_accounts[src] \u001b[38;5;241m-\u001b[39m\u001b[38;5;241m=\u001b[39m amount\n\u001b[1;32m 9\u001b[0m bank_accounts[dst] \u001b[38;5;241m+\u001b[39m\u001b[38;5;241m=\u001b[39m amount\n",
"\u001b[0;31mKeyError\u001b[0m: 'w'"
]
}
],
"source": [
"transfer(\"w\", \"z\", 10) # there is no \"w\" bank account\n",
"bank_accounts"
]
},
{
"cell_type": "code",
"execution_count": 9,
"id": "f193975b-6f75-4c3c-b789-c494ad1130a6",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"transferred\n",
"is it locked inside the with? True\n",
"is it locked after the with? False\n"
]
},
{
"data": {
"text/plain": [
"{'x': 5, 'y': 170, 'z': 150}"
]
},
"execution_count": 9,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"transfer(\"z\", \"y\", 50)\n",
"bank_accounts"
]
},
{
"cell_type": "code",
"execution_count": null,
"id": "cd9dd92a-3d2c-47c7-85f1-4bec952d1a67",
"metadata": {},
"outputs": [],
"source": []
}
],
"metadata": {
"kernelspec": {
"display_name": "Python 3.13-nogil",
"language": "python",
"name": "python3.13-nogil"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 3
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3",
"version": "3.13.2"
}
},
"nbformat": 4,
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}