Notes | numpy-07 Slice and index

#%%
import numpy as np

a = np.arange(10) # 0~10,  Not included 10
a
#%%
s = slice(2, 8, 2) #  Construct slice objects 
print(s, type(s))  # slice(2, 7, 2) <class 'slice'>
a[s] #  From the index 2 Start   Indexes 8 end ( Not included 8)  step 2
#%%
#  Slice parameters can be separated by colons  start:stop:step  To perform the slicing operation 
a[2:8:2] #  From the index 2 Start   Indexes 8 end ( Not included 8)  step 2
#%%
a[5]  #  Get only one element ,  The element index is 5
#%%
a[5:]  #  Get multiple elements ,  From the index 5 Start to finish 
#%%
a[2:5]  #  Get multiple elements ,  From the index 2 Start to index 5( Not included 5)
#%%
#  Multidimensional arrays 
import numpy as np

a = np.array([
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
])

a
#%%
#  Start cutting from an index 
a[1:] #  Index from row 1 Start to finish ,  Get all columns 
#%%
#  Slices can also include ellipsis  …, Make the length of the selection tuple the same as the dimension of the array .  If you use an ellipsis at the line position , It will return the that contains the elements in the row  ndarray
a[...,1] #  The second column of all rows ( Column index 1)
#%%
a[1,...] #  And  a[1:]  Different ,  Only the row index is obtained here 1 All columns of ,  When you return, you will first r after c Handle 
#%%
a[...,1:] #  It can also be cut + Leche   Index of all rows 1( Second column ) To the last column  (3r2c)
#%%