从坐标和[duplicate]构建numpy数组的最快方法

np.bincount .

>>> import numpy as np                                                   
>>>                                                                                                                 
>>> coords = [(0, 0), (1, 1), (0, 0)]                                       
>>> 
>>> shp = np.max(coords, axis=0) + 1     
>>> flt = np.ravel_multi_index(np.moveaxis(coords, -1, 0), shp)               
>>> result = np.bincount(flt, minlength=shp.prod()).reshape(shp)                         
>>>                                                                                                                 
>>> result                                                                                                          
array([[2, 0],                                                                                                      
       [0, 1]])                                                                                                     

正如@MikeMiller所指出的 moveaxis 在这里是过度杀戮; np.transpose(coords) 或者坐标恰好是一个数组 coords.T 移动轴 coords 因为某种原因 2D

使用 np.unique() 计算唯一坐标的数目( 但是,我不知道这是不是最快的方法 ,则不是,请参见下面的计时):

import numpy as np

a = [(0,0), (1,1), (1,0), (0,0)]

b = np.array(a)
u, c = np.unique(b, axis=0, return_counts=True)
m = np.max(b)+1
ans = np.zeros((m, m))
ans[u[:,0], u[:,1]] = c

# ans
array([[ 2.,  0.],
       [ 1.,  1.]])

我做了一些计时:

# data preparation
max_coord = 10000
max_size = 100000

# this is awful, I know it can be done much better...
coords = [(int(np.random.randint(max_coord, size=1)),
           int(np.random.randint(max_coord, size=1))) for _ in range(max_size)]

# timings using %timeit

# my solution
139 ms ± 592 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

# Paul Panzer's solution
142 ms ± 461 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

# with max_size = 1000000
# my solution
827 ms ± 19.6 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

# Paul's solution
748 ms ± 4.62 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

几乎一样(虽然我不知道他们的记忆足迹;具有 max_size=1000000 max_coord=100000 两种解决方案都给出 MemoryError