“>”不“方法，包装”和“廉政”

Question

的实例之间支持我必须安装在Windows 7版本的Python 3.6.2，我得到以下错误：

TypeError: '>' not supported between instances of 'method-wrapper' and 'int'

哪有我解决这个问题？

# create a subclass and override the handler methods 
class MyHTMLParser(HTMLParser): 
    # function to handle an opening tag in the doc 
    # this will be called when the closing ">" of the tag is reached 
    def handle_starttag(self, tag, attrs): 
     pos = self.getpos() # returns a tuple indication line and character 
     print ("At line: ", pos[0], " position ", pos[1]) 
     if attrs. __len__ > 0: 
      print ("\tAttributes: ") 
      for a in attrs: 
       print ("\t", a[0], "=", a[1]) 

Answer 1

所有__len__首先不是一个属性，它是一种方法，而你需要调用它是这样的：attrs.__len__()。但是，为什么在有非常好的方法时调用dunder方法 - len - 使用起来更简单，需要的字符更少？

if len(attrs): 
    ...