google python class上的练习
一个是统计文件中每个单词出现次数的，注意在用for line in f获取每行的字符的时候，为了从该行字符中提取单独的单词需要用split()方法。
sorted(iterable[, key][, reverse])
Return a new sorted list from the items in iterable.，
sorted返回的是一个排好序的list
因此可以slicing，而dict是不可以slicing 的
def word_count_dict(filename):
f=open(filename,'rU')
dict={}
for line in f:
for word in line.split():
word=word.lower()
if word in dict:
dict[word]+=1
else:
dict[word]=1
f.close()
return dict
def print_words(filename):
word_count=word_count_dict(filename)
words=sorted(word_count.keys())
for word in words:
print(word,word_count[word])
def get_count(word_count_tuple):
return word_count_tuple[1]
def print_top(filename):
word_count=word_count_tuple(filename)
dict1=sorted(word_count.items(),key=get_count,reverse=True)
for item in dict1[:20]:
print(item[0],item[1])
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