code: def affix_stemmer(words, exception_list=exceptions, strip_pref = True, strip_suf = True):
      
  
      for i, w in enumerate(words):
  
          try:
              words[i] = exception_list[w]
  
          except:
              if len(w) <= 4:
                  continue
  
              word = w
  
              if strip_pref:
  
                  for prefix in PREFIXES:
                      if word.startswith(prefix):
                          word = word[len(prefix):]
                          break
  
              if strip_suf:
  
                  for en in ENDS:
  
                      if len(word) <= 4:
                          break
  
                      # Strip suffixes
                      for suffix in SUFFIXES:
  
                          if len(suffix) <= len(en):
                              break
  
                          if (word + en).endswith(suffix):
                              word = word[:-len(suffix) + len(en)]
                              break
  
                      if len(word) <= 4:
                          break
  
              words[i] = word
  
      return " ".join(words)
docs: :param words: string list
  
      The affix stemmer works by rule-based stripping. It can work on prefixes,
  
      >>> affix_stemmer(['yesterday', 'yesterdom', 'yisterweek'])
      'day dom week'
  
      suffixes,
  
      >>> affix_stemmer(['likingnes', 'armlich', 'heighli'])
      'liking arm heigh'
  
      or both
  
      >>> affix_stemmer(['yisterdayes'])
      'day'
  
      You can also define whether the stemmer will strip suffixes
  
      >>> affix_stemmer(['yisterdayes'], strip_suf = False)
      'dayes'
  
      or prefixes
  
      >>> affix_stemmer(['yisterdayes'], strip_pref = False)
      'yisterday'
  
      The stemmer also accepts a user-defined dictionary, that essentially serves
      the function of a dictionary look-up stemmer
  
      >>> affix_stemmer(['arisnesse'], exception_list = {'arisnesse':'rise'})
      'rise'
  
      :exception_list:
      :return: string