python检查字符串是否是正确的ISBN，pythonisbn,def isISBN(i

python检查字符串是否是正确的ISBN，pythonisbn,def isISBN(i

def isISBN(isbn):      """Checks if the passed string is a valid ISBN number."""      if len(isbn) != 10 or not isbn[:9].isdigit():          return False      if not (isbn[9].isdigit() or isbn[9].lower() == "x"):          return False      tot = sum((10 - i) * int(c) for i, c in enumerate(isbn[:-1]))      checksum = (11 - tot % 11) % 11      if isbn[9] == 'X' or isbn[9] == 'x':          return checksum == 10      else:          return checksum == int(isbn[9])  ok = """031234161X 0525949488 076360013X 0671027360 0803612079         0307263118 0684856093 0767916565 0071392319 1400032806 0765305240"""  for code in ok.split():      assert isISBN(code)  bad = """0312341613 052594948X 0763600138 0671027364 080361207X 0307263110          0684856092 0767916567 0071392318 1400032801 0765305241 031234161          076530Y241 068485609Y"""  for code in bad.split():      assert not isISBN(code)  print "Tests of isISBN()passed."