实现Python中最常用的五种相似度度量方式

源网址http://dataconomy.com/2015/04/implementing-the-five-most-popular-similarity-measures-in-python/

1. Euclidean distance
2. Manhattan distance
3. Minkowski distance
4. Cosine similaraity
5. Jaccard similarity

代码：similaritymeasures.py

#!/usr/bin/env python
  
from math import*
from decimal import Decimal
  
class Similarity():
  
  """ Five similarity measures function """
  
  def euclidean_distance(self,x,y):
  
   """ return euclidean distance between two lists """
  
   return sqrt(sum(pow(a-b,2) for a, b in zip(x, y)))
  
  def manhattan_distance(self,x,y):
  
   """ return manhattan distance between two lists """
  
   return sum(abs(a-b) for a,b in zip(x,y))
  
  def minkowski_distance(self,x,y,p_value):
  
   """ return minkowski distance between two lists """
  
   return self.nth_root(sum(pow(abs(a-b),p_value) for a,b in zip(x, y)),p_value)
  
  def nth_root(self,value, n_root):
  
   """ returns the n_root of an value """
  
   root_value = 1/float(n_root)
   return round (Decimal(value) ** Decimal(root_value),3)
  
  def cosine_similarity(self,x,y):
  
   """ return cosine similarity between two lists """
  
   numerator = sum(a*b for a,b in zip(x,y))
   denominator = self.square_rooted(x)*self.square_rooted(y)
   return round(numerator/float(denominator),3)
  
  def square_rooted(self,x):
  
   """ return 3 rounded square rooted value """
  
   return round(sqrt(sum([a*a for a in x])),3)
  
  def jaccard_similarity(self,x,y):
  
   """ returns the jaccard similarity between two lists """
  
   intersection_cardinality = len(set.intersection(*[set(x), set(y)]))
   union_cardinality = len(set.union(*[set(x), set(y)]))
   return intersection_cardinality/float(union_cardinality)

使用方法：

#!/usr/bin/env python
  
from similaritymeasures import Similarity
  
def main():
  
  """ main function to create Similarity class instance and get use of it """
  
  measures = Similarity()
  
  print measures.euclidean_distance([0,3,4,5],[7,6,3,-1])
  print measures.jaccard_similarity([0,1,2,5,6],[0,2,3,5,7,9])
  
if __name__ == "__main__":
  main()