fo=open('test.txt','r')a=fo.read()exc={
   'the','a','to','of','and','in','that','on',''}a=a.lower()for i in ',.':    a=a.replace(i,' ')words=a.split(' ')print(words)dic={}keys=set(words)keys=keys-excprint (keys)for i in keys:    dic[i]=words.count(i)print(dic)wc=list(dic.items())wc.sort(key=lambda x:x[1],reverse=True)print(dic)for i in range(20):     print(wc[i])fo.close()

运行结果：