问numpy python:为另一列中的每个唯一值从列中找到最高值

EN

# Lex-sort combining cols-1,3 with col-3 setting the primary order
sidx = np.lexsort(a[:,[1,3]].T)

# Indices at intervals change for column-3. These would essentially 
# tell us the last indices for each group in a lex-sorted array
idx = np.append(np.flatnonzero(a[1:,3] > a[:-1,3]), a.shape[0]-1)    

# Finally, index into idx with lex-sorted indices to give us 
# the last indices in a lex-sorted version, which is equivalent 
# of picking up the highest of each group
out = a[sidx[idx]]

In [234]: a  # Input array
Out[234]: 
array([[ 25,  29,  19,  93],
       [ 27,  59,  14,  93],
       [ 24,  46,  15,  93],
       [ 79,  87,  50, 139],
       [ 13,  86,  32, 139],
       [ 56,  25,  85, 142],
       [ 62,  62,  68, 142],
       [ 27,  25,  20, 150],
       [ 29,  53,  71, 150],
       [ 64,  67,  21, 150],
       [ 96,  57,  73, 150]])

In [235]: out    # Output array
Out[235]: 
array([[ 27,  59,  14,  93],
       [ 79,  87,  50, 139],
       [ 62,  62,  68, 142],
       [ 64,  67,  21, 150]])

In [240]: np.may_share_memory(a,a[:,[1,3]])
Out[240]: False

In [241]: np.may_share_memory(a,a[:,1::2])
Out[241]: True