import re
zen="""
The Zen of Python, by Tim Peters
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
此处略去15行...
Namespaces are one honking great idea -- let"s do more of those!
"""
s=re.findall("[a-zA-Z]+",zen)
counts={}
for w in s:
counts[w]=counts.get(w,0)+1
items=list(counts.items())
items.sort(key=lambda x:x[1],reverse=True)
for i in range(20):
word,count=items[i]
print("{0:<15}{1:>5}".format(word,count))
此题综合利用正则式、字典、列表、lambda等，很典型很实用，我出试卷的必考题
