Introducing arrays

Introduzione a 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

Introduzione a NumPy

NumPy arrays

 

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

Introduzione a NumPy

Importing NumPy

 

import numpy as np
Introduzione a 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
Introduzione a 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]])
Introduzione a 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]
Introduzione a NumPy

Creating arrays from scratch

 

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

  • np.zeros()
  • np.random.random()
  • np.arange()
Introduzione a 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.]])
Introduzione a 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

Introduzione a 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

Introduzione a NumPy

Let's practice!

Introduzione a NumPy

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