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NumPy

Numpy, Numerical Python, is a powerful and supercharged library in python for handling multidimensional array objects. It offers tools for working with these arrays. Numpy can perform mathematical as well as logical operation on arrays, shape manipulation using fourier transforms and routines and it also has built in functions for random number generation and linear algebra.

Installing NumPy

Python distribution doesn't come with NumPy package. The best way to install numpy is to use pip command,

pip install numpy

To check whether the NumPy package is installed properly in your machine, try to import it from the Python prompt. We have used "as" keyword here to alias NumPy package with the name "np".

In [1]:

import numpy as np

An error message will be prompted if it is not installed properly.

Why NumPy?

Why we want to go for NumPy arrays? Why we can't simply use Python List for these numerical computations? There are some benefits when using NumPy instead of List.

NumPy arrays consumes less memory compared to List.
It is faster for performing scientific computing problems.
It is easy to use.

Lets see one example program to prove that NumPy arrays consumes less memory compared to List

In [10]:

# Importing the required packages.
import sys
import time
import numpy as np

# NumPy array with 1000 elements
numpy_array = np.arange(1000)

# Python List with 1000 elements (0 to 999)
list = range(0, 1000)

# Size of NumPy array and Python List
print("Size of numpy_array: \n", numpy_array.itemsize * numpy_array.itemsize)
print("Size of list: \n", sys.getsizeof(1)*len(list))

Size of numpy_array: 
 16
Size of list: 
 28000

NumPy Arrays

NumPy array is the central data structure of the NumPy library. It is an N-dimensional array type called ndarray. Let's now jump into the specialities of NumPy arrays.

Creating NumPy Arrays

To create a NumPy array, np.array() function can be used, All you need to do is pass a list to it, and optionally, you can also specify the data type of the data.

In [9]:

import numpy as np

list = [24, 10, 2019]

# np.array object converts list into NumpPy array
numpy_array1 = np.array(list)
print("List converted into a numpy array : \n", numpy_array1)

# Above operation can be combined without declaring list
numpy_array2 = np.array([17, 11, 1999])
print("A numpy array without declaring list : \n", numpy_array2)

# NumPy array with more than one dimension
numpy_array3 = np.array([[24, 10, 2019], [17, 11, 1999]])
print("A numpy array with more than one dimension : \n", numpy_array3)

# NumPy array with datatype as complex
numpy_array4 = np.array([2, 4, 1], dtype = complex)
print("A numpy array of complex datatype : \n", numpy_array4)

List converted into a numpy array : 
 [  24   10 2019]
A numpy array without declaring list : 
 [  17   11 1999]
A numpy array with more than one dimension : 
 [[  24   10 2019]
 [  17   11 1999]]
A numpy array of complex datatype : 
 [2.+0.j 4.+0.j 1.+0.j]

There are also certain set of functions for creating NumPy arrays,

In [12]:

import numpy as np

# A 2x2 NumPy array with all zeros
numpy_array5 = np.zeros((2, 2))
print("A numpy array with all zeros : \n", numpy_array5)

# A 2x2 NumPy array with random values 
numpy_array6 = np.random.random((2, 2))
print("A numpy array with random values : \n", numpy_array6)

A numpy array with all zeros : 
 [[0. 0.]
 [0. 0.]]
A numpy array with random values : 
 [[0.06332328 0.19111232]
 [0.51840569 0.72245051]]

NumPy Array Datatypes and Attributes

Every N-dimensional array in NumPy has an associated data type object and is a grid of elements of the same type. This data type object is denoted as "dtype". The underlying information of data type object is,

Number of bytes or size of the data.
Type of the data (integer, float etc.)
Byte order of the data.
In case of structured type, the names of fields, data type of each field and part of the memory block taken by each field.
If data type is a subarray, its shape and data type.

Whenever a data-type is required in a NumPy function or method, either a dtype object or something that can be converted to one can be supplied. Such conversions are done by the dtype constructor.

np.dtype(object, align, copy)

The parameters are :

Object - To be converted to data type object.
Align - If true, adds padding to the field to make it similar to C-struct.
Copy - Makes a new copy of dtype object. If false, the result is reference to builtin data type object.

Let's see some examples,

In [19]:

import numpy as np

# A NumPy array of the type integer (int32)
numpy_array7 = np.array([24, 10])
print("Data type of the numpy array ",numpy_array7, "\n", numpy_array7.dtype)

# A NumPy array of the type float (float64)
numpy_array8 = np.array([24.10, 10.10])
print("Data type of the numpy array ",numpy_array8, "\n", numpy_array8.dtype)

# A NumPy array of the type complex (complex128)
numpy_array9 = np.array([1 + 2j, 3 + 5j])
print("Data type of the numpy array ",numpy_array9, "\n", numpy_array9.dtype)

Data type of the numpy array  [24 10] 
 int32
Data type of the numpy array  [24.1 10.1] 
 float64
Data type of the numpy array  [1.+2.j 3.+5.j] 
 complex128

Now we can list out the various attributes of NumPy arrays.

ndarray.shape - Returns the shape of NumPy arrays in a tuple consisting of array dimensions. It can also be used to resize the array.

In [25]:

import numpy as np

# Single dimension NumPy array of the size, 3
numpy_array10 = np.array([21, 11, 2019])
print("Size/Shape of single dimension numpy array, ", numpy_array10, "\n", numpy_array10.shape)

# 3x3 dimensional NumPy array
numpy_array11 = np.array([[21, 11, 2019], [22, 11, 2019], [23, 11, 2019]])
print("Size/Shape of the 3x3 dimensional numpy array, \n", numpy_array11, "\n", numpy_array11.shape)

# 2x3 dimensional NumPy array
numpy_array12 = np.array([[21, 11, 2019], [22, 11, 2019]])
print(numpy_array12.shape, " dimensional numpy array before resizing \n", numpy_array12)
# Resizing 2x3 dimensional array into a 3x2 dimensional array
numpy_array12.shape = (3, 2)
print("Size/Shape of the numpy array after resizing it \n", numpy_array12.shape)
print("Numpy array after resizing it into 3x2 dimension \n", numpy_array12)

Size/Shape of single dimension numpy array,  [  21   11 2019] 
 (3,)
Size/Shape of the 3x3 dimensional numpy array, 
 [[  21   11 2019]
 [  22   11 2019]
 [  23   11 2019]] 
 (3, 3)
(2, 3)  dimensional numpy array before resizing 
 [[  21   11 2019]
 [  22   11 2019]]
Size/Shape of the numpy array after resizing it 
 (3, 2)
Numpy array after resizing it into 3x2 dimension 
 [[  21   11]
 [2019   22]
 [  11 2019]]

ndarray.ndim - The "ndim" attribute returns the dimension of a NumPy array.

In [33]:

import numpy as np

numpy_array13 = np.array([[10, 11], [12, 13]])
# numpy_array13.ndim returns dimension for the numpy array, numpy_array13
print("A numpy array \n", numpy_array13, "\nwith its dimension as \n", numpy_array13.ndim)

A numpy array 
 [[10 11]
 [12 13]] 
with its dimension as 
 2

numpy.itemsize - This array attribute returns the length of each element of array in bytes.

In [35]:

import numpy as np

# Second argument which is dtype which means the items datatype, and it is int8. 
# That means the bytes of each character is 1.
numpy_array14 = np.array([24, 10, 2019], dtype = np.int8)
print(numpy_array14.itemsize)

In [37]:

# Numpy array of data type float32
numpy_array15 = np.array([24, 10, 2019], dtype = np.float32) 
print(numpy_array15.itemsize)

Initialising Different NumPy Arrays

A NumPy array can be initialised in several ways,

numpy.empty - It creates an uninitialized array of specified shape and dtype. The elements in an array show random values as they are not initialized.

We have already covered functions "np.zeros" and "np.random.random" in the array creation section.

In [38]:

import numpy as np

# Generates a 2x2 dimensional numpy array with random values
numpy_array16 = np.empty([2, 2], dtype = int)
print(numpy_array16)

[[10 11]
 [12 13]]

numpy.ones - Returns a new array of specified size and type, filled with ones.

In [39]:

import numpy as np 

# Generates a 2x2 dimensional array filled with ones
numpy_array17 = np.ones([2,2], dtype = int) 
print(numpy_array17)

[[1 1]
 [1 1]]

numpy.arange - Returns an ndarray object containing evenly spaced values within a given range. Syntax as "numpy.arange(start, stop, step, dtype)"

In [40]:

import numpy as np

# A numpy array starting from 0 to 9
numpy_array18 = np.arange(10)
print("A numpy array with range 5 \n", numpy_array18)

# A numpy array starting from 1 to 10 (excluding 10) with 2 as spacing between values
numpy_array19 = np.arange(1, 10, 2)
print("A numpy array with start, stop and step parameters \n", numpy_array19)

A numpy array with range 5 
 [0 1 2 3 4 5 6 7 8 9]
A numpy array with start, stop and step parameters 
 [1 3 5 7 9]

Data Manipulation using NumPy Arrays

Let's list down the various set of routines available in NumPy package for manipulation of elements in ndarray object. They can be classified into different categories.

Basic operations.
copyto - Copies values from one array to another, broadcasting as necessary.
Changing array shape.
reshape - Gives a new shape to an array without changing its data.
ravel - Return a contiguous flattened array.
flat - A 1-D iterator over the array.
flatten - Return a copy of the array collapsed into one dimension.
Transpose like operations.
transpose - Permute the dimensions of an array.
rollaxis - Roll the specified axis backwards, until it lies in a given position.
swapaxes - Interchange two axes of an array.
Changing number of dimensions.
broadcast - Produces an object that mimics broadcasting.
broadcast_to - Broadcasts an array to a new shape.
expand_dims - Expands the shape of an array.
squeeze - Removes single-dimensional entries from the shape of an array.
Joining arrays.
concatenate - Joins a sequence of arrays along an existing axis.
stack - Joins a sequence of arrays along a new axis.
hstack - Stacks arrays in sequence horizontally (column wise).
vstack - Stacks arrays in sequence vertically (row wise).
Splitting arrays.
split - Split an array into multiple sub-arrays.
hsplit - Split an array into multiple sub-arrays horizontally (column-wise).
vsplit - Split an array into multiple sub-arrays vertically (row-wise).
Adding and removing array elements.
resize - Return a new array with the specified shape.
append - Append values to the end of an array.
insert - Insert values along the given axis before the given indices.
delete - Return a new array with sub-arrays along an axis deleted.
unique - Find the unique elements of an array.

Array Indexing and Slicing

Numpy offers several ways to index into arrays. Contents of ndarray object can be accessed and modified by indexing or slicing, just like Python's in-built container objects. Slicing is an extension of Python's basic concept of slicing to n dimensions. Note that, ndarray object follows zero-based index.

In [3]:

import numpy as np

# A numpy array of elements from 0 to 9
numpy_array20 = np.arange(10)
print("Numpy array before slicing \n", numpy_array20)
# Slicing elements from 1 to 4 from the numpy array
sliced_index = slice(1,5)
# Numpy array after slicing elements from 1 to 4
print("Numpy array after slicing \n", numpy_array20[sliced_index])

Numpy array before slicing 
 [0 1 2 3 4 5 6 7 8 9]
Numpy array after slicing 
 [1 2 3 4]

Sometimes arrays may be in multidimensional format, then we need to specify a slice for each dimension of array for accessing the corresponding elements.

In [4]:

import numpy as np

# Creates 3x4 dimensional numpy array
numpy_array21 = np.array([[24, 25, 26, 27], [28, 29, 30, 31], [32, 33, 34, 35]])
print("Numpy array before slicing \n", numpy_array21)
# Creates a subarray by slicing the first 2 rows and columns 1 and 2
sliced_array = numpy_array21[:2, 1:3]
print("Numpy array after slicing \n", sliced_array)

Numpy array before slicing 
 [[24 25 26 27]
 [28 29 30 31]
 [32 33 34 35]]
Numpy array after slicing 
 [[25 26]
 [29 30]]

Mixing integer indexing with slice indexing allows us to flexibly access elements from NumPy arrays. This will yield array of lower rank than the original array.

In [16]:

import numpy as np

# A 3x4 dimensional numpy array
numpy_array22 = np.array([[24, 25, 26, 27], [28, 29, 30, 31], [32, 33, 34, 35]])
print("Numpy array before slicing \n", numpy_array22)
# All column values in the first row
sliced_array1 = numpy_array22[0, :]
print("First row of the array with all column values \n", sliced_array1)
# All column values in the first and second row 
sliced_array2 = numpy_array22[0:2, :]
print("First two rows of the array with all column values \n", sliced_array2)

# Same distinction can be applied when accessing columns of an array
# First column of the array with all row values
sliced_array3 = numpy_array22[:, 0]
print("First column of the array with all row values \n", sliced_array3)
# First two columns of the array with all row values
sliced_array4 = numpy_array22[:, 0:2]
print("First two columns of the array with all row values \n", sliced_array4)

Numpy array before slicing 
 [[24 25 26 27]
 [28 29 30 31]
 [32 33 34 35]]
First row of the array with all column values 
 [24 25 26 27]
First two rows of the array with all column values 
 [[24 25 26 27]
 [28 29 30 31]]
First column of the array with all row values 
 [24 28 32]
First two columns of the array with all row values 
 [[24 25]
 [28 29]
 [32 33]]

Integer Array Indexing

This involves the method of selecting any arbitrary item in an array based on its N dimensional index. Integer array indexing allows you to construct these arbitrary arrays using the data from another array. In the below given example, one element of specified column from each row of ndarray object is selected. Hence, the row index contains all row numbers, and the column index specifies the element to be selected.

In [19]:

import numpy as np

numpy_array23 = np.array([[24, 25],[26, 27],[28, 29]])
print("Numpy array before integer indexing \n", numpy_array23)
# Selecting elements at (0, 1), (0, 0) and (2, 1) from the numpy_array23.
indexed_array1 = numpy_array23[[0, 0, 2], [1, 0, 1]]
print("Selecting elements at (0, 1), (0, 0) and (2, 1) from the numpy_array23 \n", indexed_array1)

numpy_array24 = np.array([[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]])
print("Numpy array before integer indexing \n", numpy_array24)
# Row indices are (0, 0) and (1, 1)
rows_array = np.array([[0, 0], [1, 1]])
columns_array = np.array([[1, 0], [0, 1]])
indexed_array2 = numpy_array24[rows_array, columns_array]
print("Indexed array \n", indexed_array2)

Numpy array before integer indexing 
 [[24 25]
 [26 27]
 [28 29]]
Selecting elements at (0, 1), (0, 0) and (2, 1) from the numpy_array23 
 [25 24 29]
Numpy array before integer indexing 
 [[24 25 26]
 [27 28 29]
 [30 31 32]
 [33 34 35]]
Indexed array 
 [[25 24]
 [27 28]]

Boolean Array Indexing

Boolean array indexing will help us to select elements from a NumPy array that satisfy some condition. Conditions can be single as well as multiple.

In [20]:

import numpy as np

numpy_array25 = np.array([[24, 25, 26], [27, 28, 29], [30, 31, 32], [33, 34, 35]])
print("Numpy array before boolean indexing \n", numpy_array25)
print("Numpy array with elements grater than 30 \n", numpy_array25[numpy_array25 > 30])

Numpy array before boolean indexing 
 [[24 25 26]
 [27 28 29]
 [30 31 32]
 [33 34 35]]
Numpy array with elements grater than 30 
 [31 32 33 34 35]

Operations in NumPy Arrays

Bitwise and String Operators

There are Bitwise functions and String functions available in the NumPy package for handling basic set of operations. Bitwise operations are,

bitwise_and - Computes bitwise AND operation of array elements.
bitwise_or - Computes bitwise OR operation of array elements.
invert - Computes bitwise NOT.
left_shift - Shifts bits of a binary representation to the left.
right_shift - Shifts bits of binary representation to the right.

List of String functions available in NumPy package are,

add - Returns element-wise string concatenation for two arrays of str or Unicode.
multiply - Returns the string with multiple concatenation, element-wise.
center - Returns a copy of the given string with elements centered in a string of specified length.
capitalize - Returns a copy of the string with only the first character capitalized.
title - Returns the element-wise title cased version of the string or unicode.
lower - Returns an array with the elements converted to lowercase.
upper - Returns an array with the elements converted to uppercase.
split - Returns a list of the words in the string, using separat or delimiter.
join - Returns a string which is the concatenation of the strings in the sequence.
replace - Returns a copy of the string with all occurrences of substring replaced by the new string.

Arithmetical and Mathematical Operations

NumPy package is having various kinds of mathematical and arithmetical operations. Fundamental mathematical functions operate elementwise on arrays and are available both operator overloads and as functions in the NumPy module. Fundamental arithmetical operations are,

add
subtract
multiply
divide

In [22]:

import numpy as np

# Creates a 3x3 dimensional numpy array with numbers from 0 to 8
numpy_array26 = np.arange(9).reshape(3, 3)
print("First numpy array \n", numpy_array26)

# Creates a single dimension numpy array
numpy_array27 = np.array([5, 5, 5])
print("Second numpy array \n", numpy_array27)

print("Adding two numpy arrays \n", np.add(numpy_array26, numpy_array27))
print("Subtracting two numpy arrays \n", np.subtract(numpy_array26, numpy_array27))
print("Multiplying two numpy arrays \n", np.multiply(numpy_array26, numpy_array27))
print("Dividing two numpy arrays \n", np.divide(numpy_array26, numpy_array27))

First numpy array 
 [[0 1 2]
 [3 4 5]
 [6 7 8]]
Second numpy array 
 [5 5 5]
Adding two numpy arrays 
 [[ 5  6  7]
 [ 8  9 10]
 [11 12 13]]
Subtracting two numpy arrays 
 [[-5 -4 -3]
 [-2 -1  0]
 [ 1  2  3]]
Multiplying two numpy arrays 
 [[ 0  5 10]
 [15 20 25]
 [30 35 40]]
Dividing two numpy arrays 
 [[0.  0.2 0.4]
 [0.6 0.8 1. ]
 [1.2 1.4 1.6]]

There are other set of arithmetical operations apart from the fundamental list. They are,

mod - Returns remainder of division of the corresponding elements in the input array.
power - This function treats elements in the first input array as base and returns it raised to the power of the corresponding element in the second input array.
around - Returns the value rounded to the desired precision.
floor - Returns the largest integer not grater than the input parameter.
ceil - Returns the ceiling of an input value.

In [26]:

import numpy as np

numpy_array28 = np.array([10, 20, 30])
print("First numpy array \n", numpy_array28)
numpy_array29 = np.array([4, 5, 6])
print("Second numpy array \n", numpy_array29)
numpy_array30 = np.array([24.8, 21.1, 90.4])
print("Third numpy array \n", numpy_array30)

print("Modulus after dividing the arrays \n", np.mod(numpy_array28, numpy_array29))
print("Applying power function on the first numpy array \n", np.power(numpy_array28, 2))
print("Applying around function on the third numpy array \n", np.around(numpy_array30))
print("Applying floor function on the third numpy array \n", np.floor(numpy_array30))
print("Applying ceil function on the third numpy array \n", np.ceil(numpy_array30))

First numpy array 
 [10 20 30]
Second numpy array 
 [4 5 6]
Third numpy array 
 [24.8 21.1 90.4]
Modulus after dividing the arrays 
 [2 0 0]
Applying power function on the first numpy array 
 [100 400 900]
Applying around function on the third numpy array 
 [25. 21. 90.]
Applying floor function on the third numpy array 
 [24. 21. 90.]
Applying ceil function on the third numpy array 
 [25. 22. 91.]

Statistical Functions

NumPy also supports various kinds of useful statistical functions for finding average, mean, median, minimum, maximum, standard deviation and variance from the given elements in the array.

average - Returns the weighted average of elements in an array according to their respective weight given in another array.
mean - Returns the arithmetic mean of elements in the array.
median - Returns the value separating the higher half of a data sample from the lower half.
amin - Returns the minimum from the elements in the given array.
amax - Returns the maximum from the elements in the given array.
std - Returns the square root of the average of squared deviations from mean.
var - Returns the average of squared deviations, In other words, the standard deviation is the square root of variance.

In [29]:

import numpy as np

numpy_array31 = np.arange(9)
print("First numpy array \n", numpy_array31)

print("Applying average function on the first numpy array \n", np.average(numpy_array31))
print("Applying mean function on the first numpy array \n", np.mean(numpy_array31))
print("Applying median function on the first numpy array \n", np.median(numpy_array31))
print("Applying minimum function on the first numpy array \n", np.amin(numpy_array31))
print("Applying maximum function on the first numpy array \n", np.amax(numpy_array31))
print("Applying standard deviation function on the first numpy array \n", np.std(numpy_array31))
print("Applying variance function on the first numpy array \n", np.var(numpy_array31))

First numpy array 
 [0 1 2 3 4 5 6 7 8]
Applying average function on the first numpy array 
 4.0
Applying mean function on the first numpy array 
 4.0
Applying median function on the first numpy array 
 4.0
Applying minimum function on the first numpy array 
 0
Applying maximum function on the first numpy array 
 8
Applying standard deviation function on the first numpy array 
 2.581988897471611
Applying variance function on the first numpy array 
 6.666666666666667

Linear Algebra in NumPy

NumPy package (numpy.linalg) offers all the functionality required for linear algebra. Some of the important functions in this module are described in the following list.

dot - Dot product of the two numpy arrays.
matmul - Matrix product of the two numpy arrays.
determinant - Computes the determinant of the array.

In [35]:

import numpy as np

numpy_array32 = np.array([24, 25])
numpy_array33 = np.array([26, 27])

# (24 * 26) + (25 * 27)
print("Dot product of the arrays \n", np.dot(numpy_array32, numpy_array33))

numpy_array34 = np.array([[24, 25], [26, 27]])
numpy_array35 = np.array([[28, 29], [30, 31]])
print("Matrix Multiplication of the arrays \n", np.matmul(numpy_array34, numpy_array35))

print("Determinant of the 2x2 dimensional array [[28, 29], [30, 31]] \n", np.linalg.det(numpy_array35))

Dot product of the arrays 
 1299
Matrix Multiplication of the arrays 
 [[1422 1471]
 [1538 1591]]
Determinant of the 2x2 dimensional array [[28, 29], [30, 31]] 
 -1.9999999999999931

Array Broadcasting in NumPy

Arrays with different sizes cannot be added, subtracted, or generally be used in arithmetic. A way to overcome this is to duplicate the smaller array so that it is the dimensionality and size as the larger array. This is called array broadcasting and is available in NumPy when performing array arithmetic, which can greatly reduce and simplify your code.

Broadcasting is the name given to the method that NumPy uses to allow array arithmetic between arrays with a different shape or size. It solves the problem of arithmetic between arrays of differing shapes by in effect replicating the smaller array along the last mismatched dimension.

Broadcasting two arrays together follows these rules:

If the arrays do not have the same rank, prepend the shape of the lower rank array with 1s until both shapes have the same length.
The two arrays are said to be compatible in a dimension if they have the same size in the dimension, or if one of the arrays has size 1 in that dimension.
The arrays can be broadcast together if they are compatible in all dimensions.
After broadcasting, each array behaves as if it had shape equal to the elementwise maximum of shapes of the two input arrays.
In any dimension where one array had size 1 and the other array had size greater than 1, the first array behaves as if it were copied along that dimension.

In [41]:

import numpy as np

# One dimensional numpy array
numpy_array36 = np.array([24, 25, 26])
print("One dimensional numpy array \n", numpy_array36)
value = 3
print("Scalar value \n", value)
print("Resulted array after adding a scalar value and one dimensional numpy array \n", (numpy_array36 + value)) 

# Two dimensional numpy array
numpy_array37 = np.array([[24, 25, 26], [27, 28, 29]])
print("Two dimensional numpy array \n", numpy_array37)
print("Resulted array after adding a scalar value and two dimensional numpy array \n", (numpy_array37 + value))
print("Resulted array after adding one dimensional numpy array and two dimensional numpy array \n", (numpy_array36 + numpy_array37))

One dimensional numpy array 
 [24 25 26]
Scalar value 
 3
Resulted array after adding a scalar value and one dimensional numpy array 
 [27 28 29]
Two dimensional numpy array 
 [[24 25 26]
 [27 28 29]]
Resulted array after adding a scalar value and two dimensional numpy array 
 [[27 28 29]
 [30 31 32]]
Resulted array after adding one dimensional numpy array and two dimensional numpy array 
 [[48 50 52]
 [51 53 55]]

Image Operations in NumPy

NumPy provides a high-performance multidimensional array and basic tools to compute with and manipulate these arrays. "SciPy" builds on this, and provides a large number of functions that operate on numpy arrays and are useful for different types of scientific and engineering applications.

SciPy provides some basic functions to work with images. For example, it has functions to read images from disk into numpy arrays, to write numpy arrays to disk as images, and to resize images. Here is a simple example that showcases these functions.

In [57]:

from scipy.misc import imread, imsave, imresize
from IPython.display import Image

# Reading a JPEG image into a numpy array
img = imread('2020.jpg')
print("Datatype of the image \n", img.dtype)
print("Shape of the image \n", img.shape)

# We can tint the image by scaling each of the color channels
# by a different scalar constant. The image has shape (400, 248, 3);
# we multiply it by the array [1, 0.95, 0.9] of shape (3,);
# numpy broadcasting means that this leaves the red channel unchanged,
# and multiplies the green and blue channels by 0.95 and 0.9
# respectively.
img_tinted = img * [1, 2, 3]

# Resize the tinted image to be 300 by 300 pixels.
img_tinted = imresize(img_tinted, (300, 300))

# Write the tinted image back to disk
imsave('2020_modified.jpg', img_tinted)

Datatype of the image 
 uint8
Shape of the image 
 (683, 1024, 3)

C:\Anaconda\lib\site-packages\scipy\misc\pilutil.py:482: FutureWarning: Conversion of the second argument of issubdtype from `int` to `np.signedinteger` is deprecated. In future, it will be treated as `np.int32 == np.dtype(int).type`.
  if issubdtype(ts, int):
C:\Anaconda\lib\site-packages\scipy\misc\pilutil.py:485: FutureWarning: Conversion of the second argument of issubdtype from `float` to `np.floating` is deprecated. In future, it will be treated as `np.float64 == np.dtype(float).type`.
  elif issubdtype(type(size), float):