Selecting a sub array from a NumPy array (Slicing)
To get a sub-array, we pass a slice in place of the element index.
Syntax:
numpyArr[x:y]
Here x and y are the starting and last index of the required sub-array.
Example:
Python3
import numpy as np # NumPy Array numpyArr = np.array([ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]) # the slice 3:6 is passed instead # of index print ( "Sub-Array=" , numpyArr[ 3 : 6 ]) |
Output:
Sub-Array= [4 5 6]
A sub-array starting from the 3rd index up to the 6th index ( excluding the last the 6th index ) was selected. You can slice a sub-array starting from the first element by leaving the starting index blank.
Example: The following code selects a sub-array starting from the first element.
Python3
import numpy as np numpyArr = np.array([ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]) # works same as 0:6 print ( "Sub-Array=" , numpyArr[: 6 ]) |
Output:
Sub-Array= [1 2 3 4 5 6]
Similarly, leaving the left side of the colon blank will give you an array up to the last element.
Example: The following code selects a sub-array starting from a particular index up to the last index.
Python3
import numpy as np numpyArr = np.array([ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]) # same as 3:9 or 3:n, where n is # the length of array print ( "Sub-Array=" , numpyArr[ 3 :]) |
Output:
Sub-Array= [4 5 6 7 8 9]
Select an element or sub array by index from a Numpy Array
The elements of a NumPy array are indexed just like normal arrays. The index of the first element will be 0 and the last element will be indexed n-1, where n is the total number of elements.
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