2.4. Array Attributes

2.4.1. Dimensions

import numpy as np


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

a.shape         # (3,)
a.ndim          # 1
a.size          # 3
len(a)          # 3

import numpy as np


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

a.shape         # (2, 3)
a.ndim          # 2
a.size          # 6
len(a)          # 2

import numpy as np


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

a.shape         # (3, 3)
a.ndim          # 2
a.size          # 9
len(a)          # 3

import numpy as np


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

              [[11, 22, 33],
               [44, 55, 66],
               [77, 88, 99]]])

a.shape         # (2, 3, 3)
a.ndim          # 3
a.size          # 18
len(a)          # 2

2.4.2. Data

• int64 takes 64 bits (8 bytes of memory)

• strides inform how many bytes numpy has to jump to access values in each dimensions

import numpy as np


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

a.shape         # (3,)
a.itemsize      # 8
a.strides       # (8,)
a.data          # <memory at 0x10cdfaa10>
list(a.data)    # NotImplementedError: multi-dimensional sub-views are not implemented

import numpy as np


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

a.shape         # (2, 3)
a.itemsize      # 8
a.strides       # (24, 8)
a.data          # <memory at 0x10caefbb0>

import numpy as np


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

a.shape         # (3, 3)
a.itemsize      # 8
a.strides       # (24, 8)
a.data          # <memory at 0x10cf92210>

import numpy as np


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

              [[11, 22, 33],
               [44, 55, 66],
               [77, 88, 99]]])

a.shape         # (2, 3, 3)
a.itemsize      # 8
a.strides       # (72, 24, 8)
a.data          # <memory at 0x107933c70>

2.4.3. Assignments

2.4.3.1. Numpy Attributes

• Assignment: Numpy Attributes

• Last update: 2020-10-01

• Complexity level: easy

• Lines of code to write: 4 lines

• Estimated time of completion: 3 min

• Filename: solution/numpy_attributes.py

English:

1. Use data from "Given" section (see below)

2. Print:

   • number of dimensions;

   • number of elements;

   • data type;

   • element size;

   • shape;

   • strides.

Polish:

1. Użyj danych z sekcji "Given" (patrz poniżej)

2. Wypisz:

   • liczbę wymiarów,

   • liczbę elementów,

   • typ danych,

   • rozmiar elementu,

   • kształt,

   • przeskoki (strides).

Given:

a = np.array([[-1.1, 0.0, 1.1],
              [ 2.2, 3.3, 4.4]])