Importing NumPy:

import numpy as np

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NumPy array vs Python array:

a = np.array([3, 4, 5])
b = np.array([4, 9, 7])
a + b

output:

array([ 7, 13, 12])

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Two-dimensional NumPy array/ matrix

x = np.array([[1, 2], [3, 4]])
x

output:

array([[1, 2], 
	   [3, 4]])

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Number of dimensions in a NumPy array

x.ndim

output:

2

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Data type stored within the array

x.dtype

output:

dtype('int64')

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Number of rows and columns respectively

x.shape

output:

(2, 2)

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Finding the sum of a NumPy array

x.sum()

output:

np.int64(10)

same thing:

np.sum(x)

output:

np.int64(10)

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Reshaping an array:

x = np.array([1, 2, 3, 4, 5, 6])
x

output:

array([1, 2, 3, 4, 5, 6])

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x = x.reshape((3, 2))
x

output:

array([[1, 2], 
	   [3, 4], 
	   [5, 6]])

• Note: NumPy arrays are specified as a sequence of rows, row-major ordering, as opposed to column-major ordering.