TCO for python 3.7

tco.py

from dataclasses import dataclass, field
from functools import wraps


@dataclass
class _TCOCall:
    args: list = field(default_factory=list)
    kwargs: dict = field(default_factory=dict)


def tco(f):
    first_call = True

    @wraps(f)
    def wrapper(*args, **kwargs):
        nonlocal first_call
        
        r = _TCOCall(args, kwargs)
        
        if first_call:
            first_call = False
            while isinstance(r, _TCOCall):
                r = f(*r.args, **r.kwargs)
            first_call = True
        return r
    return wrapper