decoder.py

#!/usr/bin/env python3
"""Decoder -- Program 13 from "Marvel Super Heroes Computer Fun".

Faithful recreation of the type-in BASIC listing: inverts the Program 12
encoder. Strip blanks from input, swap '*' back to space, then for I=1..5,
J=0..MM-1 read MM$[I+J*5] -- walks the 5-char column blocks back into rows.
Type one coded line at a time (uppercase); type STOP to finish.

    python decoder.py
"""
import os
import sys

GREEN = "\033[32m"
RESET = "\033[0m"
CLEAR = "\033[2J\033[H"


def enable_ansi():
    if os.name == "nt":
        os.system("")


def decode(M):                                  # lines 170-300
    MM = ""
    for ch in M:                                 # 170-220
        if ch == " ":
            continue                             # 190
        MM += " " if ch == "*" else ch           # 200
    mm = len(MM) // 5                            # 230
    A = ""
    for I in range(1, 6):                        # 240
        for J in range(0, mm):                   # 250
            A += MM[I + J * 5 - 1]               # 260 (1-based MID$ -> 0-based index)
    return A


def play():
    enable_ansi()
    sys.stdout.write(CLEAR + GREEN)
    print("ENTER MESSAGE")
    print()
    while True:
        try:
            line = input("? ").strip().upper()
        except (EOFError, KeyboardInterrupt):
            break
        if line == "STOP":                       # 160
            break
        if not line:
            continue
        print()
        print("DECODED MESSAGE:")
        print()
        print(decode(line))
        print()
        print()
    sys.stdout.write(RESET)


def main():
    play()


if __name__ == "__main__":
    try:
        main()
    except KeyboardInterrupt:
        sys.stdout.write(RESET + "\n")