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| #!/usr/bin/env python3 | |
| import argparse, os.path, string, sys | |
| def parseArgs(): | |
| parser = argparse.ArgumentParser( | |
| description='A small, simple encrypter and decrypter.') | |
| parser.add_argument('keys', nargs='+', | |
| help='variable number of keys to encrypt with') | |
| parser.add_argument('-i', '--infile', | |
| help='file to optionally read from instead of stdin') | |
| parser.add_argument('-o', '--outfile', | |
| help='file to optionally write to instead of stdout') | |
| parser.add_argument('-d', '--decrypt', action='store_true', | |
| help='decrypt text instead of encrypting it') | |
| return parser.parse_args() | |
| def charToInt(char): | |
| return string.ascii_letters.index(char) | |
| def intToChar(index): | |
| return string.ascii_letters[index % len(string.ascii_letters)] | |
| def getText(infile): | |
| if infile == None: | |
| return sys.stdin.read() | |
| else: | |
| try: | |
| with open(infile, 'r') as f: | |
| return f.read() | |
| except IOError: | |
| print('error reading from file:', infile) | |
| raise SystemExit | |
| def putText(outfile, text): | |
| if outfile == None: | |
| print(text) | |
| else: | |
| try: | |
| with open(outfile, 'w') as f: | |
| f.write(text.rstrip() + '\n') | |
| except IOError: | |
| print('error writing to file:', infile) | |
| def operate(decrypt, text, keys): | |
| result = '' | |
| for i, c in enumerate(text): | |
| if c not in string.ascii_letters: | |
| result += c | |
| continue | |
| index = charToInt(c) | |
| for key in keys: | |
| k = key[i % len(key)] | |
| if decrypt: | |
| index -= charToInt(k) | |
| else: | |
| index += charToInt(k) | |
| result += intToChar(index) | |
| return result | |
| def main(): | |
| args = parseArgs() | |
| text = getText(args.infile) | |
| text = operate(args.decrypt, text, args.keys) | |
| putText(args.outfile, text) | |
| if __name__ == '__main__': | |
| main() |
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