converting between "base ten" and "base T"

base_ten_base_T.py

# Python code accompanying https://ddrake.prose.sh/base_ten_without_zero

def T_to_zero(Tnum):
    """Convert a number (provided as a string) written with "T" notation
    to a Python integer, which by default is displayed using the
    ordinary positional notation with "0".
    """
    T_digit_to_int = {str(i): i for i in range(1, 10)}
    T_digit_to_int['T'] = 10
    return sum(10**p * T_digit_to_int[d] for p, d in enumerate(reversed(Tnum)))


def zero_to_T(x):
    """Convert a number (a positive Python int) into "T" notation."""
    if x == 0:
        return ""
    else:
        r = x % 10
        r_ = r if r > 0 else 10
        y = (x - r_) // 10
        int_to_T_digit = {i: str(i) for i in range(1, 10)}
        int_to_T_digit[0] = 'T'
        return zero_to_T(y) + int_to_T_digit[r]