An ICP Python Canister Development Kit and Application Framework. Write decentralized applications in Python efficiently on the Internet Computer.
Live demo: https://ic-basilisk.tech/.
- icp-cli (
curl --proto '=https' --tlsv1.2 -LsSf https://github.com/dfinity/icp-cli/releases/latest/download/icp-cli-installer.sh | sh) - Python 3.10+
To create a simple "Hello World" project with icp-cli, run:
# 1. Scaffold a new project from the Basilisk template
icp new my_project --git https://github.com/smart-social-contracts/basilisk --subfolder icp-cli/templates/hello-world
# 2. Install dependencies and deploy to the local replica
cd my_project
# Optional: python -m venv venv && source venv/bin/activate
pip install -r requirements.txt
icp network start -d
icp deploy
# 3. Call your canister
icp canister call my_project greet '("World")'
# ("Hello, World!")Alternatively, you can install Basilisk directly: pip install ic-basilisk
- Based on CPython 3.13, compiled to WASM — deploy in seconds with a pre-built template, no Rust toolchain needed
- Near-complete standard library —
os,json,re,math,datetime,hashlib,collections, networking stubs, and more. A few modules requiring native OS threads or sockets (e.g.threading,subprocess,socket) are not available
Built-in Application Framework:
- Persistent storage — Rust-backed stable data structures (
StableBTreeMap,StableBTreeSet,StableVec,StableLog,StableCell,StableMinHeap) powered byic-stable-structureswith tagged binary encoding — data persists across canister upgrades with no serialization step. Supports explicit type hints (nat8,int32, etc.) for compact, correctly-ordered keys and values - Filesystem — standard
open()andoscalls, automatically persisted to stable memory across upgrades - IC system APIs —
ic.caller(),ic.time(),ic.canister_balance(), inter-canister calls, timers, and Candid types (Principal,Record,Variant, etc.)
Interactive shell, ORM, Schema Upgrade Checking, file transfer, task management, wallet, and more are provided by ic-basilisk-toolkit (
pip install ic-basilisk-toolkit).
┌─────────────────────────────────────────────────────────┐
│ Basilisk CDK │
├─────────────┬────────────┬──────────────────────────────┤
│ Filesystem │ Storage │ IC System APIs │
│ POSIX-like │ BTreeMap, │ Timers, Inter-canister calls │
│ os/open() │ Vec, Log, │ Candid types, Lifecycle │
│ auto-persist│ Cell, Heap │ │
├─────────────┴────────────┴──────────────────────────────┤
│ MemoryManager (ic-stable-structures) │
├─────────────────────────────────────────────────────────┤
│ CPython 3.13 (compiled to WASM) │
├─────────────────────────────────────────────────────────┤
│ Internet Computer (ICP) │
└─────────────────────────────────────────────────────────┘
Basilisk can auto-inject standardized __shell__ and __browse__ endpoints into your canister at build time. Enable them with a single line:
__basilisk_features__ = ["shell", "browse"]__shell__ — full Python execution (controller-only @update):
icp canister call my_canister __shell__ '("print(1 + 1)")'
# ("2\n")__browse__ — read-only data introspection (public @query, instant, free):
# Discover data schema
icp canister call my_canister __browse__ '("{\"action\": \"schema\"}")'
# Read keys from a stable map (paginated, default limit=100)
icp canister call my_canister __browse__ '("{\"action\": \"keys\", \"map\": \"users\"}")'
# Get a specific value
icp canister call my_canister __browse__ '("{\"action\": \"get\", \"map\": \"users\", \"key\": \"alice\"}")'Both endpoints can be overridden with custom implementations (e.g. custom guards, filtered data access). If you define __shell__ or __browse__ yourself, the compiler uses yours instead of the default.
| CPython 3.13 | RustPython | |
|---|---|---|
| Build time | ~seconds (template) | ~60-120s (Cargo build) |
| Wasm size | ~5.3 MB | ~26 MB |
| Python compatibility | Full (reference implementation) | Partial (~3.10) |
Pure-compute benchmarks comparing Rust, Motoko, and CPython on identical algorithms. Measured via ic0.performance_counter on a PocketIC replica. On the IC, 1 instruction ≈ 1 cycle of compute cost. Lower is better. These numbers exclude the fixed per-call fee (~590K cycles for updates, ~260K for queries) and memory/storage costs.
| Benchmark | Rust | Motoko | CPython | vs Rust (CPython) |
|---|---|---|---|---|
| noop (call overhead) | 13,686 | 3,299 | 15,592 | 1.1x |
| increment (state mutation) | 12,827 | 3,411 | 15,159 | 1.2x |
| fibonacci(25) (iterative) | 12,750 | 5,713 | 36,553 | 2.9x |
| fibonacci_recursive(20) | 373,953 | 2,050,048 | 29,617,193 | 79.2x |
| sum_to(10000) (arithmetic loop) | 272,761 | 513,314 | 12,767,523 | 46.8x |
| ackermann(3,6) (deep recursion) | 3,285,678 | 15,225,081 | 284,158,839 | 86.5x |
| method_overhead (total prelude) | 12,334 | 2,863 | 10,172 | 0.8x |
Full CI logs: All backends
These benchmarks use language-specific data structures (Python dict, list, str) so they only compare CPython against RustPython — not against Rust/Motoko, which have fundamentally different standard libraries.
| Benchmark | CPython | RustPython | RustPython / CPython |
|---|---|---|---|
| string_ops (100 concatenations) | 275,375 | 2,135,202 | 7.8x |
| list_ops (500 append + sort) | 602,711 | 5,819,267 | 9.7x |
| dict_ops (500 inserts + lookups) | 3,407,101 | 23,087,720 | 6.8x |
CPython is 6–10x faster than RustPython across the board, with the gap largest for recursive function calls and list operations.
Run it yourself: trigger the Benchmark workflow from the Actions tab — select
cpython,rust,motoko, orallas the backend, andlocaloricas the network.
The benchmark sources are in benchmarks/counter/ (CPython), benchmarks/counter_rust/ (Rust), and benchmarks/counter_motoko/ (Motoko).
- Realms — Governance Operating System for building and deploying governance systems on the Internet Computer
Using Basilisk? Open a PR to add your project here.
A basilisk fountain in Basel, Switzerland — where this project was written.
This project was written in Basel, Switzerland — a city guarded by basilisks since the Middle Ages. In European mythology, the basilisk is the king of serpents — part rooster, part snake — making it a fitting patron for a Python framework.
According to local legend, a basilisk once dwelt beneath Basel's streets, turning to stone anyone who dared look upon it. The citizens, unable to defeat it by force, outwitted the creature with a mirror: confronted with its own reflection, the basilisk was petrified by its own gaze. Impressed by the creature's power, the people of Basel didn't destroy it — they adopted it. To this day, basilisk statues stand watch over the city's fountains, their water said to carry a faint enchantment of protection.
In the shadow of the Tower of the Bank for International Settlements — where the world's central banks convene to shape global finance — a basilisk fountain stands watch. It is here, at the crossroads of ancient myth and modern power, that we chose to unleash the dormant power of Python onto the Internet Computer.
The fountains still flow in Basel. And now, so does Python on the IC. Great power requires great responsibility. Handle with care.
Basilisk may have unknown security vulnerabilities due to the following:
- Limited or no production deployments on the IC
- No extensive automated property tests
- No independent security reviews/audits
See SECURITY.md.
For detailed architecture notes, see CPYTHON_MIGRATION_NOTES.md.
Feel free to open issues.
See LICENSE.