Introducing arrays

Giới thiệu về NumPy

Izzy Weber

Core Curriculum Manager, DataCamp

NumPy and the Python ecosystem

A graphic of Atlas holding up the globe, styled as NumPy since NumPy holds up the Python world

Giới thiệu về NumPy

NumPy arrays

 

graphics of 1D, 2D, and 3D arrays

Giới thiệu về NumPy

Importing NumPy

 

import numpy as np
Giới thiệu về NumPy

Creating 1D arrays from lists

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

array([3, 2, 5, 8, 4, 9, 7, 6, 1])

 

type(array)

numpy.ndarray
Giới thiệu về NumPy

Creating 2D arrays from lists

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

array([[3, 2, 5],
       [9, 7, 1],
       [4, 3, 6]])
Giới thiệu về NumPy

Python lists

  • Can contain many different data types
python_list = ["beep", False, 56, .945, [3, 2, 5]]

 

NumPy arrays

  • Can contain only a single data type
  • Use less space in memory
numpy_boolean_array = [[True, False], [True, True], [False, True]]

numpy_float_array = [1.9, 5.4, 8.8, 3.6, 3.2]
Giới thiệu về NumPy

Creating arrays from scratch

 

There are many NumPy functions used to create arrays from scratch, including:

  • np.zeros()
  • np.random.random()
  • np.arange()
Giới thiệu về NumPy

Creating arrays: np.zeros()

np.zeros((5, 3))

array([[0., 0., 0.],
       [0., 0., 0.],
       [0., 0., 0.],
       [0., 0., 0.],
       [0., 0., 0.]])
Giới thiệu về NumPy

Creating arrays: np.random.random()

np.random.random((2, 4))

array([[0.88524516, 0.85641352, 0.33463107, 0.53337117],
       [0.69933362, 0.09295327, 0.93616428, 0.03601592]])

 

np.random is a NumPy module while np.random.random()is a function within np.random

Giới thiệu về NumPy

Creating arrays with np.arange()

np.arange(-3, 4)

array([-3, -2, -1,  0,  1,  2,  3])

np.arange(4)

array([0, 1, 2, 3])

np.arange(-3, 4, 3)

array([-3,  0,  3])

from matplotlib import pyplot as plt
plt.scatter(np.arange(0, 7),
            np.arange(-3, 4))
plt.show()

A plot of two range arrays on the X and Y axes

Giới thiệu về NumPy

Let's practice!

Giới thiệu về NumPy

Preparing Video For Download...