[Python] 全角文字を半角文字へ変換する

コード

import functools
import re

def bytesToInt(b):
  return int(b.hex(), 16)

def intToBytes(i):
  return bytes.fromhex(f"{i:x}")

def getDiff(c1, c2):
  e1 = c1.encode()
  e2 = c2.encode()
  return bytesToInt(e1) - bytesToInt(e2)

def exchange(match, diff):
  r = bytesToInt(match[0].encode()) - diff
  return intToBytes(r).decode()

exchange1 = functools.partial(exchange, diff=0xEFBC60)
exchange2 = functools.partial(exchange, diff=0xEFBD20)

def wideStringToHalfString(c):
  pat1 = re.compile("[！-／０-９：-＠Ａ-Ｚ［-＿]")
  pat2 = re.compile("[ａ-ｚ｀｛-～]")
  t = pat1.sub(exchange1, c)
  return pat2.sub(exchange2, t)

if __name__ == "__main__":
  data = [
    "！＂＃＄％＆＇（）＊＋，－．／",
    "０１２３４５６７８９",
    "：；＜＝＞？＠",
    "ＡＢＣＤＥＦＧＨＩＪＫＬＭＮＯＰＱＲＳＴＵＶＷＸＹＺ",
    "［＼］＾＿",
    "ａｂｃｄｅｆｇｈｉｊｋｌｍｎｏｐｑｒｓｔｕｖｗｘｙｚ",
    "｀｛｜｝～",
  ]

  print(f"{getDiff('！', '!'):X}")
  print(f"{getDiff('０', '0'):X}")
  print(f"{getDiff('：', ':'):X}")
  print(f"{getDiff('Ａ', 'A'):X}")
  print(f"{getDiff('［', '['):X}")
  print(f"{getDiff('＿', '_'):X}")
  print(f"{getDiff('ａ', 'a'):X}")
  print(f"{getDiff('｀', '`'):X}")  # 並びがおかしい?
  print(f"{getDiff('｛', '{'):X}")

  print("".join(data))
  r = wideStringToHalfString("".join(data))
  print(r)