{
"cells": [
{
"cell_type": "code",
"execution_count": 1,
"id": "3b8d1ed9-9568-473e-bfa2-3b08f9e4587f",
"metadata": {},
"outputs": [],
"source": [
"import threading\n",
"import time"
]
},
{
"cell_type": "code",
"execution_count": 2,
"id": "da885575-cedf-4bb4-8bbd-44400974d3f8",
"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": "ceeb7904-ff2c-424c-bf7c-724d1b285e3b",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"CPU times: user 133 ms, sys: 144 μs, total: 133 ms\n",
"Wall time: 129 ms\n"
]
},
{
"data": {
"text/plain": [
"2000000"
]
},
"execution_count": 3,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"%%time\n",
"# 133 ms with no locks\n",
"# 348 ms with locks (fine grained)\n",
"# 124 ms with locks (coarse grained)\n",
"\n",
"lock = threading.Lock() # this protects the \"total\" variable\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",
"\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": 3,
"id": "042356c8-7d34-4fa5-bef1-0c43e829fc13",
"metadata": {},
"outputs": [],
"source": [
"import threading\n",
"\n",
"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, and release after the with statement\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(\"locked inside with?\", lock.locked())\n",
" print(\"locked after with?\", lock.locked())"
]
},
{
"cell_type": "code",
"execution_count": 4,
"id": "1878620a-553b-4f25-9606-1e2605b318ac",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"transferred\n",
"locked inside with? True\n",
"locked after with? False\n"
]
}
],
"source": [
"transfer(\"x\", \"y\", 20)"
]
},
{
"cell_type": "code",
"execution_count": 5,
"id": "8901ec24-7471-40e1-8182-585d3cc760c7",
"metadata": {},
"outputs": [
{
"data": {
"text/plain": [
"{'x': 5, 'y': 120, 'z': 200}"
]
},
"execution_count": 5,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"bank_accounts"
]
},
{
"cell_type": "code",
"execution_count": 6,
"id": "9cee2370-0f3d-4ac0-930a-c59f9f0d7f1b",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"denied\n",
"locked inside with? True\n",
"locked after with? False\n"
]
}
],
"source": [
"transfer(\"x\", \"z\", 10)"
]
},
{
"cell_type": "code",
"execution_count": 7,
"id": "3a583c7c-57a3-4f42-8301-8ce601a2249e",
"metadata": {},
"outputs": [
{
"data": {
"text/plain": [
"{'x': 5, 'y': 120, 'z': 200}"
]
},
"execution_count": 7,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"bank_accounts"
]
},
{
"cell_type": "code",
"execution_count": 8,
"id": "3346b86d-5f80-4007-8879-b452c4826c50",
"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\n",
"Cell \u001b[0;32mIn[3], line 9\u001b[0m, in \u001b[0;36mtransfer\u001b[0;34m(src, dst, amount)\u001b[0m\n\u001b[1;32m 7\u001b[0m \u001b[38;5;28;01mwith\u001b[39;00m lock:\n\u001b[1;32m 8\u001b[0m success \u001b[38;5;241m=\u001b[39m \u001b[38;5;28;01mFalse\u001b[39;00m\n\u001b[0;32m----> 9\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 10\u001b[0m bank_accounts[src] \u001b[38;5;241m-\u001b[39m\u001b[38;5;241m=\u001b[39m amount\n\u001b[1;32m 11\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)"
]
},
{
"cell_type": "code",
"execution_count": 9,
"id": "02262baa-6f4f-455e-b913-accfa894cc18",
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"transferred\n",
"locked inside with? True\n",
"locked after with? False\n"
]
}
],
"source": [
"transfer(\"z\", \"x\", 3)"
]
},
{
"cell_type": "code",
"execution_count": 10,
"id": "1b338a2c-1274-41e8-9179-89b797e4ec2f",
"metadata": {},
"outputs": [
{
"data": {
"text/plain": [
"{'x': 8, 'y': 120, 'z': 197}"
]
},
"execution_count": 10,
"metadata": {},
"output_type": "execute_result"
}
],
"source": [
"bank_accounts"
]
}
],
"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,
"nbformat_minor": 5
}