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Accessing a value in a NumPy 2D array
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schedule Jul 1, 2022
Last updated Python●NumPy
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expand_more To access a value in a Numpy 2D array, use the []
syntax.
Suppose we have the following 2D Numpy array:
x = np.array([[1,2,3], [4,5,6]])x
array([[1, 2, 3], [4, 5, 6]])
Accessing a value
To access the value residing at row 0 column 1 (i.e. the value 2):
x[0,1]
2
To access the value residing at row 1 column 2 (i.e. the value 6):
x[1,2]
6
WARNING
Do not use [][]
syntax
In this previous code snippet, we could have used x[1][2]
instead of x[1,2]
, which would also return the value 6. However, it is not good practice to use double []
s in Numpy. x[1][2]
involves two steps: firstly accessing row 1 (i.e. [4,5,6]
), and then accessing the 2nd index (i.e. 6). On the other hand, x[1,2]
involves just one step, that is, the value is directly fetched, and is therefore faster than double []
s.
Published by Isshin Inada
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