Continuous code improvement

#  ! /Usr/bin/ENV Python  #  -*-Coding: UTF-8 -*-  #  Factory Model  Def Createdomtree (htmlstream, type = '  Soup  '  ):  If Type = "  Soup  "  : Return  Tndomtreewithsoup (htmlstream)  If Type = "  Lxml  "  :  Return  Tndomtreewithlxml (htmlstream)  Return  None  #  External dependent interface, which shields the third-party library I use  Class  Tndomtree: #  Public      Def   _ Init __  (Self, htmlstream): self.html stream = Htmlstream  Def  Getlinklist (Self ):  Return Self. _ getelementbytagname ( '  A  ' ) #  Extracts the common behavior of sub-classes to the base class          Def Getimagelist (Self ):  Return Self. _ getelementbytagname ( '  IMG  ' ) #  Extracts the common behavior of sub-classes to the base class          Def  Elementtostring (self, element ):  Pass          Def  Getattrvalueofelement (self, element, attname ):  Pass          #  Private     Def _ Getelementbytagname (self, tagname ): #  Subclass implementation of this method          Pass  #  Use beautifulsoup class  From Beautifulsoup Import  Beautifulsoup  Class  Tndomtreewithsoup (tndomtree ):  Def   _ Init __  (Self, htmlstream): tndomtree.  _ Init __ (Self, htmlstream) self. _ tree = Beautifulsoup(self.html Stream)  Def  _ Getelementbytagname (self, tagname ):  Return  Self. _ tree. findall (tagname)  Def  Elementtostring (self, element ):  Return  STR (element)  Def  Getattrvalueofelement (self, element, attname ):  If Hasattr (element, attname ):  Return  STR (element [attname])  Else  :  Return   ""  #  Use lxml  From Lxml.html Import  Tostring  From Lxml.html. soupparser Import  Fromstring Class  Tndomtreewithlxml (tndomtree ):  Def   _ Init __  (Self, htmlstream): tndomtree.  _ Init __  (Self, htmlstream) self. _ tree = Fromstring(self.html Stream)  Def  _ Getelementbytagname (self, tagname): List = []  For I In Self. _ tree. ITER ():  If I. Tag = Tagname: List. append (I)  Return  List  Def  Elementtostring (self, element ):  Return  Tostring (element)  Def  Getattrvalueofelement (self, element, attname ):  If Attname In Set (element. Keys ()):  Return  STR (element. attrib [attname])  Else  :  Return   ""  If   _ Name __ = "  _ Main __  "  : S1 = ''' <P> beiai </P> <p>  </P>  '''      Print  S1 domtree = Createdomtree (S1, '  Soup  '  ) List = Domtree. getimagelist ()  For I In  List:  Print Domtree. getattrvalueofelement (I,'  SRC  '  )  Print Domtree. elementtostring (I)

Why can I extract a public interface? Essentially, these things are similar, but specificCodeYou should design APIs similar to other classes. Otherwise, the class design is wrong.