计算ngram距离-python实现【转载】

def Ngram_distance(str1, str2, n=2):
    tmp = ‘ ‘ * (n-1)
    str1 = tmp + str1 + tmp#表示以首字母开头和本char结尾
    str2 = tmp + str2 + tmp
    set1 = set([str1[i:i+n] for i in range(len(str1)-(n-1))])
    set2 = set([str2[i:i+n] for i in range(len(str2)-(n-1))])
    setx = set1 & set2
    len1 = len(set1)
    len2 = len(set2)
    lenx = len(setx)
    num_dist = len1 + len2 - 2*lenx
    num_sim = 1 - num_dist / (len1 + len2)
    return set1,set2,{‘dist‘: num_dist, ‘sim‘: num_sim}

print(Ngram_distance(‘girl‘,‘girlfriend‘))

({‘gi‘, ‘ir‘, ‘rl‘, ‘l ‘, ‘ g‘}, 
{‘gi‘, ‘en‘, ‘d ‘, ‘ir‘, ‘lf‘, ‘ie‘, ‘rl‘, ‘fr‘, ‘ri‘, ‘ g‘, ‘nd‘}, {‘dist‘: 8, ‘sim‘: 0.5})