gistfile1.py

from jinja2.runtime import Undefined

SPECIAL_DELIM = [("[{}[".format("="*n), "]{}]".format("="*n)) for n in range(10)]

def type_of(v, *types):
    return any(isinstance(v, t) for t in types)

def get_delim(s):
    if '"' not in s and "\n" not in s and "\\" not in s:
        return ('"', '"')
    for op, cl in SPECIAL_DELIM:
        if op not in s and cl not in s:
            if s.startswith("\n"):
                op += "\n" # Newlines at the start of long strings are ignored
            return (op, cl)
    raise ValueError("could not find delimiter for string")

def indent(s, level, prefix="  "):
    return "\n".join("{}{}".format(prefix*level, l).rstrip()
                     for l in s.split("\n"))

def to_lua(v):
    if v == None or isinstance(v, Undefined):
        return "nil"
    elif type_of(v, bool):
        return v and "true" or "false"
    elif type_of(v, str):
        od, cd = get_delim(v)
        return "{}{}{}".format(od, v, cd)
    elif type_of(v, float, int):
        return "{}".format(v)
    elif type_of(v, dict):
        kvs = []
        for k, v in v.iteritems():
            ks = "{}".format(to_lua(k))
            if ks.startswith("["):
                ks = "[ {} ]".format(ks)
            else:
                ks = "[{}]".format(ks)
            vs = to_lua(v)
            kvs.append("{} = {}".format(ks, vs))
        return "{{\n{}\n}}".format(indent(",\n".join(kvs), 1))
    elif type_of(v, list, tuple, set):
        kvs = []
        for i, v in enumerate(v):
            ks = "[{}]".format(i+1)
            vs = to_lua(v)
            kvs.append("{} = {}".format(ks, vs))
        return "{{\n{}\n}}".format(indent(",\n".join(kvs), 1))
    else:
        raise TypeError("unable to convert python value of type '{}' to lua".format(type(v)))

Need to watch out for keywords?

'and', 'break', 'do', 'else', 'elseif', 'end', 'false',
'for', 'function', 'goto', 'if', 'in', 'local', 'nil', 'not', 'or', 'repeat',
'return', 'then', 'true', 'until', 'while'

Need to watch out for keywords?

Nope; table keys are always of the form between [ and ]

Awesome! I'm glad you found this useful. :)