solpython

A Python-to-EVM compiler written entirely in Solidity. Feed it Python source code as a string, get EVM-compatible bytecode out — no off-chain tooling required.

644 tests across 46 test suites.

Architecture

Six-phase compiler pipeline, each phase implemented as a Solidity contract:

Python source (string)
       │
       ▼
  ┌──────────┐
  │  Lexer   │  Tokenizes source into token stream
  └────┬─────┘
       │ Token[]
       ▼
  ┌──────────┐
  │  Parser  │  Recursive descent → AST (struct array in storage)
  └────┬─────┘
       │ ASTNode[]
       ▼
  ┌───────────────┐
  │   Semantic    │  Symbol table, scope resolution, type inference
  │   Analyzer    │
  └────┬──────────┘
       │
       ▼
  ┌───────────────┐
  │     Code      │  AST → custom stack-based bytecode
  │   Generator   │
  └────┬──────────┘
       │ bytes (bytecode)
       ▼
  ┌──────────┐
  │    VM    │  Stack machine executes bytecode
  └──────────┘

Alternative backends:

• Solidity Backend — AST → Solidity source code transpiler
• Yul Backend — AST → Yul IR transpiler

Supported Python Features

Core:

• Integer arithmetic (+, -, *, /, //, %, **) with negative numbers
• Augmented assignment (+=, -=, *=, /=)
• Comparisons (==, !=, <, >, <=, >=, is, is not)
• Chained comparisons (a < b < c)
• Boolean operators (and, or, not)
• Ternary expressions (a if cond else b)
• if / elif / else
• while loops
• for loops with range(), list iteration, break, continue
• for...else / while...else
• Function definitions with recursion, default parameters, keyword arguments
• Nested function definitions
• return statements
• pass statement

Data Types:

• Integers (tagged, -2^62 to 2^62-1)
• Booleans (True, False) with proper tagging
• None type with safety checks
• Strings with methods (upper, lower, split, contains, charAt, slice)
• Lists with indexing, negative indexing, len(), append()
• Dicts with string/int keys, items(), values(), get(), update()
• Sets with add(), remove(), in operator
• Tuples with unpacking (a, b = 1, 2)
• Float (6-digit fixed-point)

Builtins:

• print() — integer and string output
• len(), type(), isinstance()
• range(), enumerate(), zip()
• map(), filter()
• sorted(), reversed()
• abs(), min(), max()
• f-strings and %s/%d formatting

Advanced:

• try / except / finally / raise
• class with methods, self, single inheritance
• import / from...import with static linking
• global / nonlocal keywords
• Virtual file system (VFS) for module loading
• Garbage collection (reference counting)
• Constant folding and dead code elimination
• Structured error messages with line/column info

Build & Test

Requires Foundry.

forge build          # compile
forge test           # run all 644 tests
forge test -vvv      # verbose output
forge test --match-test testFibonacci   # run a single test

Example

def fib(n):
    if n <= 1:
        return n
    return fib(n - 1) + fib(n - 2)

print(fib(10))  # → 55

This compiles to bytecode that runs entirely on-chain via the Solidity VM contract.

Project Structure

src/
  types/                  AST node, token, and type info structs
  libraries/              String utility library
  phases/
    Lexer.sol             Tokenizer
    Parser.sol            Recursive descent parser
    SemanticAnalyzer.sol  Symbol table, scope resolution
    CodeGenerator.sol     AST → bytecode
    VM.sol                Stack-based bytecode interpreter
    SolidityBackend.sol   AST → Solidity source transpiler
    YulBackend.sol        AST → Yul IR transpiler
  optimizer/
    ConstantFolder.sol    Compile-time constant folding
  gc/
    RefCounter.sol        Reference counting GC
  vfs/
    VFS.sol               Virtual file system
  venv/
    Venv.sol              Compilation environment
  PythonCompiler.sol      Top-level orchestrator

test/
  46 test suites covering lexer, parser, semantic analysis,
  code generation, VM execution, and end-to-end integration.

  Key files:
    Integration.t.sol     End-to-end compiler tests (fibonacci, fizzbuzz, bubble sort)
    E2E.t.sol             Feature-specific end-to-end tests
    TypeClassify.t.sol    Type system and tagging verification
    Exception.t.sol       Exception handling tests
    GC.t.sol              Garbage collection tests

Value Tagging

The VM uses a tagged value system to distinguish types:

Type	Tag	Range
Integer	(none)	-2^62 to 2^62-1
Boolean	BOOL_OFFSET (2^66)	2^66 (False), 2^66+1 (True)
None	NONE_VALUE	Fixed sentinel
Float	Tag at bits 252-255	6-digit fixed-point
List	ID 0 to 2^60-1	GC-tracked
Dict	ID 2^60 to 2^61-1	GC-tracked
Set	ID 2^61 to 2^62-1	GC-tracked
String	ID >= 2^62	Static + runtime

Known Limitations

• No generators/iterators
• No class inheritance beyond single-level
• No closures (inner functions cannot capture outer variables)
• Float arithmetic uses 6-digit fixed-point, not IEEE 754
• GC is reference counting only (no cycle detection)
• Solidity/Yul backends don't support all features (see BACKEND_LIMITATIONS.md)

License

MIT