Simple NumPy Array Tutorial

Simple introduction of Numpy

Numpy is the most powerful Python package for working with data.

Knowledge of Numpy is a must for Data analytics, machine learning. Numpy is a core library for scientific computing in Python. Its tools are used to solve computing problem (specifically mathematical models) of Science and Enginering. 

The most important aspect of Numpy is its n-dimensional array having significant advantage over Python Lists

1. More compact 
2. Faster access in reading and writing items 
3. More convenient
4. More efficient.

1. Create a Numpy Array

There are multiple ways of creating a Numpy Array

• array()
• ones()
• zeros()
• logspace()
• linspace()
• arange()

1.1 Creating from a Python List

# Create a one dimensional array from a list
import numpy as np
lst = [0,1,2,3,4]  #Create a List
np_arr = np.array(lst)  #Convert list to np array

1.2. Create a Two Dimensional Array(Matrix )

lst2 = [[0,1,2], [3,4,5], [6,7,8]]
numpy_2darr = np.array(lst2)

1.3. Create a Three Dimensional Array

from numpy import zeros
np.zeros((2,3,2))

1.4. Create an array using Array function 

from numpy import *
arr=array([1,2,3,4,5],int)

1.5 Create an array using linspace function

numpy.linspace(start, stop, num = 50, endpoint = True, retstep = False, dtype = None) : Returns number spaces evenly w.r.t interval.

from numpy import *
arr=linspace(0,15,5)

1.6 Create using arange function

 This is not "arrange" with double r. Its more like A Range.

from numpy import *
arr=arange(0,15,5)
arr
#will print array(0,5,10)

1.7 Create using logspace function

logspace creates array with log values. The first parameter specifies the starting point, the second ending point and the third the number of steps to reach the ending point

>>> arr=logspace(10,20,3)
>>> arr
array([1.e+10, 1.e+15, 1.e+20])

1.8 Create using one and zeros function

>>> arr=ones(10)
>>> arr
array([1., 1., 1., 1., 1., 1., 1., 1., 1., 1.])
>>> arr=zeros(10)
>>> arr
array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0.])

3. Provide a datatype for the Array

numpy_arr_2d = np.array(lst2, dtype='float')