NumPy Creating Arrays

2 D Array

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import numpy as np

arr1=np.array([1,2,3])
arr1

OUTPUT:

array([1, 2, 3])

type(arr1)

OUTPUT:

numpy.ndarray‍

arr1.ndim

OUTPUT:

1

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arr1.size

OUTPUT:

3

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arr1.shape

(3,)

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Creating 2-D Array

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

OUTPUT:

[[1 1 1]
[2 2 2]
[3 3 3]
[4 4 4]]

arr.shape

OUTPUT:

(4,3)

arr.size

OUTPUT:

12

arr.ndim

OUTPUT:

2

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Class and Attributes of nd array,Size and shape of a numpy array

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list3 = [ [1, 2, 3, 4],[5, 6, 7, 8], [9, 10, 11, 12] ]

arr = np.array(list3, dtype ='str')
print(arr)

OUTPUT:

[['1' '2' '3' '4']
['5' '6' '7' '8']
['9' '10' '11' '12']]

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arr.dtype

OUTPUT:

dtype('<U2')

arr.size

OUTPUT:

12

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arr.ndim

OUTPUT:

2

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Accessing 2-D array Indexing

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list3 = [[1, 2, 3, 4],[5, 6, 7, 8], [9, 10, 11, 12]]

arr = np.array(list3)

print(arr)

OUTPUT:

[[ 1  2  3  4]
[ 5  6 7  8]
[ 9 10 11 12]]

‍

‍

arr[ 0:2 , 2:4 ]

OUTPUT:

array([[3, 4],
      [7, 8]])

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print("First Row:",arr[0])
print("Last Row:",arr[-1])
print("Single Element",arr[2,3])
print("All Rows but Second colums",arr[:,2])
print("Second Row and all colums",arr[2,:])
print("All rows but only columns from 1 to 3\n",arr[:,1:3])

OUTPUT:

First Row: [1 2 3 4]
Last Row: [ 9 10 11 12]
Single Element 12
All Rows but Second colums [ 3  7 11]
Second Row and all colums [ 9 10 11 12]
All rows but only columns from 1 to 3
[[ 2  3]
[ 6  7]
[10 11]]