pdist()是一个计算距离的函数，得到的是一个对称矩阵，其中对角线为0。squareform()函数是对pdist()函数返回的矩阵的上三角形进行处理，然后从第一行开始取值，返回一个数组，变成一个稀疏矩阵，同时spuareform（）函数还可以进行逆运算，把一个稀疏矩阵生成一个非稀疏矩阵。比如：欧氏距离，计算欧氏距离的例子如下：
距离计算规则如图：

 from scipy.spatial.distance import pdist, squareform
 
 x=np.random.rand(3)
 print(x)
 [0.15297464 0.24703217 0.95730516]

 y=np.random.rand(3)
 print(y)
 [0.71366508 0.36111799 0.5305526 ]

 x1=np.random.rand(5)
 print(x1)
 [0.93979333 0.21137943 0.55437114 0.15531124 0.06513814]

 y1=np.random.rand(5)
 print(y1)
 [0.17426077 0.51733583 0.93023109 0.28271652 0.40983225]

 A=np.vstack((x,y)).T
 print(A)
 [[0.15297464 0.71366508]
 [0.24703217 0.36111799]
 [0.95730516 0.5305526 ]]

 B=np.vstack((x1,y1)).T
 print(B)
 [[0.93979333 0.17426077]
 [0.21137943 0.51733583]
 [0.55437114 0.93023109]
 [0.15531124 0.28271652]
 [0.06513814 0.40983225]]

 C=np.vstack((A,B))
 print(C)
 [[0.15297464 0.71366508]
 [0.24703217 0.36111799]
 [0.95730516 0.5305526 ]
 [0.93979333 0.17426077]
 [0.21137943 0.51733583]
 [0.55437114 0.93023109]
 [0.15531124 0.28271652]
 [0.06513814 0.40983225]]

 distance=pdist(C, 'euclidean')
 print(distance)
 [0.36487843 0.82491076 0.95396051 0.20483235 0.45609208 0.43095489
 0.31627463 0.73020258 0.71751909 0.16023461 0.64679746 0.12066283
 0.18830432 0.35672193 0.74604282 0.56753741 0.83941466 0.9002974
 0.80516291 0.84855252 0.79194369 0.90582318 0.53677352 0.24122575
 0.18150354 0.7606076  0.71425758 0.1558512 ]

 D=squareform(distance)
 print(D)
 [[0.         0.36487843 0.82491076 0.95396051 0.20483235 0.45609208
  0.43095489 0.31627463]
 [0.36487843 0.         0.73020258 0.71751909 0.16023461 0.64679746
  0.12066283 0.18830432]
 [0.82491076 0.73020258 0.         0.35672193 0.74604282 0.56753741
  0.83941466 0.9002974 ]
 [0.95396051 0.71751909 0.35672193 0.         0.80516291 0.84855252
  0.79194369 0.90582318]
 [0.20483235 0.16023461 0.74604282 0.80516291 0.         0.53677352
  0.24122575 0.18150354]
 [0.45609208 0.64679746 0.56753741 0.84855252 0.53677352 0.
  0.7606076  0.71425758]
 [0.43095489 0.12066283 0.83941466 0.79194369 0.24122575 0.7606076
  0.         0.1558512 ]
 [0.31627463 0.18830432 0.9002974  0.90582318 0.18150354 0.71425758
  0.1558512  0.        ]]

 squareform(D)
 array([0.36487843, 0.82491076, 0.95396051, 0.20483235, 0.45609208,
       0.43095489, 0.31627463, 0.73020258, 0.71751909, 0.16023461,
       0.64679746, 0.12066283, 0.18830432, 0.35672193, 0.74604282,
       0.56753741, 0.83941466, 0.9002974 , 0.80516291, 0.84855252,
       0.79194369, 0.90582318, 0.53677352, 0.24122575, 0.18150354,
       0.7606076 , 0.71425758, 0.1558512 ])