一個實際的錯誤案例(Django controller)

def parse_weburl(weburl):

    index = "http%253A%252F%252F"
    if index >= 0:
        weburl = weburl[:index]

    # fix the issue for now news
    index = weburl.find('http%3A%2F%2')
    if index >= 0:
        weburl = weburl[:index]

    weburl = force_decode(weburl)

    return weburl


會造成以下error

2012-02-15 18:38:15.935
slice indices must be integers or None or have an __index__ method
Traceback (most recent call last):
  File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/webapp/_webapp25.py", line 701, in __call__
    handler.get(*groups)
  File "/base/data/home/apps/tagtoov1/1.356847196571547955/libs/handlers.py", line 332, in get
    self.get_handler(*args, **atts)
  File "/base/data/home/apps/tagtoov1/1.356847196571547955/views/ajaxs.py", line 506, in get_handler
    referer = parse_weburl(referer)
  File "/base/data/home/apps/tagtoov1/1.356847196571547955/views/ajaxs.py", line 16, in parse_weburl
    weburl = weburl[:index]
TypeError: slice indices must be integers or None or have an __index__ method

改成下面的樣式就不會error

def parse_weburl(weburl):
    index = weburl.find("http%253A%252F%252F")
    if index >= 0:
        weburl = weburl[:index]

    # fix the issue for now news
    index = weburl.find('http%3A%2F%2')
    if index >= 0:
        weburl = weburl[:index]

    weburl = force_decode(weburl)

    return weburl

注意到index 從舊版的"字串"變成"整數"