Frame words in a phrase in reverse order the non-idiomatic unpythonic way

reverse_sentence.py

# Online Python - IDE, Editor, Compiler, Interpreter
import string

EXCLUDE_CHARS = {each_invalid_char: "" for each_invalid_char in string.punctuation}
SAME_CHARS = {**{w:w for w in string.ascii_letters}, **EXCLUDE_CHARS}
EXCLUDE_CHAR_MAP = str.maketrans(SAME_CHARS)


def reverse_string(sentence: str):
    space = " "
    final_str = ""
    n = len(sentence)
    start_idx = 0
    astring = ""
    for idx in iter(lambda: start_idx, n):
        char = sentence[idx]
        if char != space:
            astring += char
        else:
            final_str = space + astring.translate(EXCLUDE_CHAR_MAP) + final_str
            astring = ""
        start_idx += 1
    if astring:
        final_str = space + astring.translate(EXCLUDE_CHAR_MAP) + final_str
    return final_str.strip()
    
print(reverse_string("The Final Countdown."))