molang

Molang to Python Translator & interpreter written in pure Python.

Installation

Install the module with pip:

pip3 install molang

Update existing installation: pip3 install molang --upgrade

Links

• Documentation
• Source Code

Requirements

Features

• Pure-Python Molang parser and AST representation
• Interpreter: evaluate Molang expressions against a runtime context
• Compiler / emitter: convert parsed AST back to Molang source
• DSL convenience objects: query, variable, math, temp, array, etc.
• Assignment support for dotted variables (e.g. variable.x = 1, temp.a.b = 2)
• Full math.* function implementations and callable math functions (e.g. math.sqrt(4))
• Function-call support in expressions and argument evaluation
• CLI to run Molang files or execute inline Molang code

See the docs for more information.

Example

Parse / Compile / Eval

Parse, compile and evaluate with a context

import molang

expr = "math.sqrt(16) + variable.x"
node = molang.parse(expr)
print(molang.compile(expr))
ctx = molang.create_context()
ctx['variable']['x'] = 9
print(molang.eval(expr, ctx))  # prints 13.0

DSL usage

from molang.dsl import variable, math, query

variable.x = 4
print(variable.x)           # MolangExpr("variable.x = 4;") when used as assignment
print(math.sqrt(variable.x))

expr = query.block_state("minecraft:cardinal_direction") == "north"
print(expr) # MolangExpr("query.block_state('minecraft:cardinal_direction') == 'north'")

Assignment to dotted variables

import molang

ctx = molang.create_context()
molang.eval('variable.health = 20', ctx)
print(ctx['variable']['health'])  # 20.0

Function calls and math helpers

import molang

ctx = molang.create_context()
print(molang.eval('math.lerp(0, 10, 0.5)', ctx))  # 5.0

Pydantic Support

from pydantic import BaseModel
from molang.dsl import MolangExpr, query

class Test(BaseModel):
  condition: MolangExpr

x = Test(condition=query.block_state("facing") == "north")
print(x.model_dump()) # {"condition": "query.block_state('facing') == 'north'"}

Command-line interface

usage: molang [-h] [-c <cmd>] [-V] [<file>]

Run molang files

positional arguments:
  <file>                execute the molang code contained in a file.

options:
  -h, --help            show this help message and exit
  -c <cmd>              execute the molang code in cmd. cmd can be one or more statements separated by newlines, with significant leading whitespace as in normal module code.
  -V, --version         print the molang version number and exit.