05 python.pdf

Dr.D.Sugumar
Associate Prof/ECE
Karunya University
PYTHON PROGRAMMING Intro

Python ( What and Why ?)
• Python is the most popular programming language & choice for
Data Scientist / Data Engineer across the world
• Very rich libraries & functions
• Community support
• Easy to deploy in production
• Support for all the new state of the art technologies ( like deep
learning)
3

Not this python,unfortunately
4

ButthisPython!
Programming Language
6

ButthisPython!
Created in 1991 by Guido van Rossum
7

ButthisPython!
Cross Platform
8

ButthisPython!
Freely Usable Even for Commercial Use
Cross Platform
9

10
"Python is easy to use, powerful, and versatile, making it a great choice
for beginners and experts alike." – codeschool.com
print("Python" +" is "+"cool!")

11

print("Python"+" is"+"cool!")
public class Main {
public static void main(String[] args) {
System.out.println("Hello world!");
}
}
12

public class Main {
public static void main(String[] args) {
System.out.println("Hello world!");
}
}
print("Hello world!")
13

14

● Python works on Windows, Linux, Mac,
Raspberry Pi, NVidia boards (linux), PYNQ
FPGA etc.
● Few lines of Programming
● Prototyping of Python programming is fast
● Syntax is same as like normal English
language
● It relies on Indentation, whitespace, scope of
loops, functions and classes
● Latest version of python is version3 (3.9).
Why Python?.

Python IDE.
IDLE : Python Software foundation license
PYCHARM: Apache license
SPYDER: MIT license

● Python is a popular programming language. It
was created by Guido van Rossum, and
released in 1991.
● Python is a programming language that lets
you work more quickly and integrate your
systems more effectively.
1. Web development
2. Handle Big data
3. Handles complex Mathematics
4. Software development
5. Connects to database systems
Python & Uses.

for beginners and experts alike." – codeschool.com/ Pluralsight Platform
18
Big names using Python

https://opencv.org/
Image Processing using Python
19

https://www.pygame.org
Game Development using Python
20

16
https://matplotlib.org/
Data Science using Python

https://github.com/amueller/word_cloud
Natural Language Processing (NLP) and Text Mining using Python
22

Top programming languages 2019 by IEEE Spectrum
2
3

Let's now explorethePythonuniverse!
24

Google Colab
• Colaboratory, or “Colab” for short, is a product from
Google Research.
• Colab allows anybody to write and execute arbitrary
python code through the browser, and is especially well
suited to machine learning, data analysis and education.
• More technically, Colab is a hosted Jupyter notebook
service that requires no setup to use, while providing free
access to computing resources including GPUs (graphics
processing unit ).

Google Colab
How to open:
'py' is a regular python file. It's plain text and contains just your code. ...
'ipynb' is a python notebook and it contains the notebook code, the execution results and
other internal settings in a specific format.

How to install Python the Anaconda way
1. Download Anaconda (which includes Python):
https://www.anaconda.com/download/
2. Run the installer and follow the installation instructions
3. Run the Spyder editor and create your first Python program "helloworld.py"
PythonSetup
30

How to install Python the Anaconda way
1. Download Anaconda (which includes Python and
relevant libraries): https://www.anaconda.com/distribution/
2. Run the installer and follow the instructions
3. Run the Spyder editor or Jupyter Notebook and create your first Python program "helloworld.py"
PythonSetup
31

Installation Steps
Install using the instruction given in the below links -
1. Install Jupyter - http://jupyter.org/install
Preferred installation method is through Anaconda distribution.
Install Python 3.8 version.
2. Anaconda 5.2 For Linux Installer - https://www.anaconda.com/download/#linux
3. Anaconda 5.2 For macOS Installer - https://www.anaconda.com/download/#macos
4. Anaconda 5.2 For Windows Installer - https://www.anaconda.com/download/#windows
(You need to download the version compatible with your OS)
32

Python Install
33
Many PCs and Macs will have python already installed.
To check if you have python installed on a Windows PC, search in the start bar for Python or run the following on
the Command Line (cmd.exe):
C:UsersYour Name>python --version
To check if you have python installed on a Linux or Mac, then on linux open the command line or on Mac open the
Terminal and type:
python --version
Python is an interpreted programming language, this means that as a developer you write Python (.py) files in a text
editor and then put those files into the python interpreter to be executed.
The way to run a python file is like this on the command line:
C:UsersYour Name>python helloworld.py

Execute Python Syntax
34
As we learned in the previous page, Python syntax can be executed by writing directly in the Command Line:
print("Hello, Karunyans!")
Hello, Karunyans!
Or by creating a python file on the server, using the .py file extension, and running it in the Command Line:
C:UsersYour Name>python myfile.py

Installing Python
IDLE
PYTHON.ORG | MICROSOFT VISUAL STUDIO

Setting Python in
Environment Varaibles to
access from Command
window

Basic Python
Programming
print(‘Hello world’)

Indentation in python!!
40
Indentation refers to the spaces at the beginning of a code line.
(Where in other programming languages the indentation in code is for readability only, the indentation in Python is very
important)
Python uses indentation to indicate a block of code.
if 5 > 2:
print("Five is greater than two!")
Python will give you an error if you skip the indentation:
if 5 > 2:
The number of spaces is up to you as a programmer, but it has to be at least one.
if 5 > 2:
if 5 > 2:
You have to use the same number of spaces in the same block of code, otherwise Python will give you an error:
if 5 > 2:
Syntax Error:

Add two number.
a = 5.4
b = 4.6
sum = float(a) + float(b)
print(sum)
User Input.
a = input(“Enter number1: “)
b = input(“Enter number2: “)
sum = int(a) + int(b)
print(“The sum of {0} and {1} is
{2}”.format(a, b, sum))

Slicing
42
b = "Hello, World!"
print(b[2:5])
b = "Hello, World!"
print(b[:5])
b = "Hello, World!"
print(b[2:])
b = "Hello, World!"
print(b[-5:-2])

43
• String is a sequence of characters, like "Python is cool"
• Each character has an index
•Accessing a character: string[index]
x = "Python i s cool"
print(x[10])
•Accessing a substring via slicing: s t r i n g [ s t a r t : f i n i s h ]
p r i n t ( x [ 2 : 6 ] )
String
P y t h o n i s c o o l
0 1 2 3 4 5 6 7 8 9 10 11 12 13

44
>>> x = "Python is cool"
>>> "cool" in x
>>> len(x)
>>> x + "?"
>>> x.upper()
# membership
# length of string x
# concatenation
# to upper case
>>> x.replace("c", "k") # replace characters in a string
StringOperations
0 1 2 3 4 5 6 7 8 9 10 11 12 13

StringOperations:Split
0 1 2 3 4 5 6 7 8 9 10 11 12 13
P y t h o n
0 1 2 3 4 5
i s
0 1
c o o l
0 1 2 3
x . s p l i t ( " " )
>>> x.split(" ") 45

>>> y = x.split(" ")
>>> ",".join(y) 40
StringOperations:Join
P y t h o n , i s , c o o l
0 1 2 3 4 5 6 7 8 9 10 11 12 13
P y t h o n
0 1 2 3 4 5
i s
0 1
c o o l
0 1 2 3
" , " . j o i n ( y )

Conditionals and Loopsin RealLife
48
Conditionals andLoops

49
• Cores of programming!
• Rely on boolean expressions which return either True or False
• 1 < 2 : True
• 1.5 >= 2.5 : False
• answer == "Computer Science" :
can be True or False depending on the value of variable answer
• Boolean expressions can be combined with: and, or, not
• 1 < 2 and 3 < 4 : True
• 1.5 >= 2.5 or 2 == 2 : True
• not 1.5 >= 2.5 : True
ConditionalsandLoops

50
Conditionals: SimpleForm
i f condition:
i f - code
else:
else- code

51
Conditionals:GenericForm
if bolean-expression-1:
code-block-1
elif boolean-expression-2:
code-block-2 (as many elif's as you want)
else:
code-block-last

If & Elif. a = 33
b = 33
if a > b:
print(“a is greater than b")
elif a == b:
print("a and b are same")
else:
print("b is greater than a")
AND | OR. a = 200
b = 33
c = 500
if a > b and c > a:
print("Both conditions are True")
#if a > b or c > a:
# print(“only one is True")

53
Conditionals:(Drivinglicenseage)
age = 20
if age < 16:
print("Not Eligible for Driving license!")
else:
print("OK, You are eligible to get your Driving license!")

54
Conditionals:usingInput()
age = int(input("Enter your age: "))
if age < 16:
print("Not Eligible for Driving license!")
else:
print("OK, You are eligible to get your Driving license!")

55
Conditionals:Grading
grade = int(raw_input("Numeric grade: "))
if grade >= 80:
print("A")
elif grade >= 65:
print("B")
elif grade >= 55:
print("C")
else:
print("E")

56
Loops
• Useful for repeating code!
• Two variants:
while boolean-expression:
code-block
for element i n collection:
code-block

While Loops
57
code-block
while input("Which is the best subject? ") != "ECE":
print("Try again!")
print("Of course it is!")

58
WhileLoops
x = 5
while x > 0:
print (x )
x -= 1
print("While loop i s over now!")
code-block

While Loops
59
code-block
while input("Which i s the best subject? " ) != "Computer Science":
print("Try again!")
print("Of course i t i s ! " )

So far, we have seen (briefly) two kinds of collections:
string and list
For loops can be used to visit each collection's element:
60
ForLoops
for element i n collection:
code-block
for chr in "string":
print(chr)
for elem in [ 1 ,3,5]:
print(elem)

While.
i = 1
while i < 20:
print(i)
i += 1
FOR.
for x in range(10):
print(x)
for x in range(1, 10):
print(x)
for x in range(1, 10, 2):
print(x)

Expression and Arithmetic
62
Assume variable a holds 10 and variable b holds 20, then −

Expression and Arithmetic
63
a = 21
b = 10
c = 0
c = a + b
print ("Line 1 - Value of c is ", c)
c = a - b
c = a * b
c = a / b
c = a % b
a = 2
b = 3
c = a**b
a = 10
b = 5
c = a//b
ref: https://realpython.com/python-operators-expressions/
Extra notes

String manipulation in python
64

• Working with data heavily involves reading and writing!
• Data come in two types:
• Text: Human readable, encoded in ASCII/UTF-8, example: .txt, .csv
• Binary: Machine readable, application-specific encoding,
example: .mp3, .mp4, .jpg
Input/Output
65

66
python
is
cool
Input
cool.txt
x = open("cool.txt", "r") # read mode
y = x.read() # read the whole
print(y)
x.close()

python
is
cool
44
Input
cool.txt
x = open("cool. t x t " , " r " )
# read l i n e by l i n e
f o r l i n e i n x :
l i n e = l i n e . r e p l a c e ( " n " , " " )
p r i n t ( l i n e )
x . close( )

68
python
is
cool
Input
cool.txt
x = open( "C: User s Desktop coo l . tx t " , " r " ) # absolute location
f o r l i n e i n x :
l i ne = l ine. r eplace(" n" , " " )
p r i n t ( l i n e )
x.close()

Output
# write mode
x = open( "cool.t x t " , "w")
x.write("and Interesting n")
x . close()
# append mode
69
x = open( "cool.t x t " , "a")
x.write(" and Interesting n ")
x . close()
Write mode overwrites files,
while append mode does not overwrite files but instead appends at the end of the files' content

72
• Functions encapsulate code blocks
• Why functions? Modularization and reuse!
• You actually have seen examples of functions:
• print()
• input()
• Generic form:
Functions
def function-name(parameters):
code-block
return value

Functions:CelciustoFahrenheit
def celsius_to_fahrenheit(celsius):
fahrenhe i t = celsiu s * 1.8 + 32.0
return fahrenheit
def function-name(parameters):
code-block
return value
74

75
Functions:DefaultandNamedParameters
def hello(name_man="Bro",name_woman="Sis"):
print("Hello, " + name_man +"&"+name_woman+ "!")
>>> hello() Hello,
Bro& Sis!
>>>hello(name_woman="Lady")
Hello, Bro & Lady!
>>> hello(name_woman=“Girls",name_man="Boys")
Hello, Boys & Girls!

Built-in Math Functions
76
x = min(5, 10, 25)
y = max(5, 10, 25)
print(x)
print(y)
x = abs(-7.25)
print(x)
x = pow(4, 3)
print(x)
import math
import math
x = math.sqrt(64)
print(x)
x = math.ceil(1.4)
y = math.floor(1.4)
print(x) # returns 2
print(y) # returns 1
x = math.pi
print(x)

77
• Code made by other people shall be reused!
• Two ways of importing modules (= Python files):
• Generic form: importmodule_name
import math
print(math.sqrt(4))
• Generic form: from module_name import function_name
from math import sqrt
p r i n t ( s q r t ( 4 ) )
Imports

Math Methods
78
Method Description
math.acos() Returns the arc cosine of a number
math.acosh() Returns the inverse hyperbolic cosine of a number
math.asin() Returns the arc sine of a number
math.asinh() Returns the inverse hyperbolic sine of a number
math.atan() Returns the arc tangent of a number in radians
math.atan2() Returns the arc tangent of y/x in radians
math.atanh() Returns the inverse hyperbolic tangent of a number
math.ceil() Rounds a number up to the nearest integer
math.comb() Returns the number of ways to choose k items from n items without
repetition and order
math.copysign() Returns a float consisting of the value of the first parameter and the sign of
the second parameter
math.cos() Returns the cosine of a number
math.cosh() Returns the hyperbolic cosine of a number
math.degrees() Converts an angle from radians to degrees
math.dist() Returns the Euclidean distance between two points (p and q), where p and q
are the coordinates of that point
math.erf() Returns the error function of a number
math.erfc() Returns the complementary error function of a number
math.exp() Returns E raised to the power of x
math.expm1() Returns E
x
- 1
math.fabs() Returns the absolute value of a number
math.factorial() Returns the factorial of a number
math.floor() Rounds a number down to the nearest integer
math.fmod() Returns the remainder of x/y
math.frexp() Returns the mantissa and the exponent, of a specified number
math.fsum() Returns the sum of all items in any iterable (tuples, arrays, lists, etc.)
math.gamma() Returns the gamma function at x
math.gcd() Returns the greatest common divisor of two integers
math.hypot() Returns the Euclidean norm
math.isclose() Checks whether two values are close to each other, or not
math.isfinite() Checks whether a number is finite or not
math.isinf() Checks whether a number is infinite or not
math.isnan() Checks whether a value is NaN (not a number) or not
math.isqrt() Rounds a square root number downwards to the nearest integer
math.ldexp() Returns the inverse of math.frexp() which is x * (2**i) of the given numbers x and i
math.lgamma() Returns the log gamma value of x
math.log() Returns the natural logarithm of a number, or the logarithm of number to base
math.log10() Returns the base-10 logarithm of x
math.log1p() Returns the natural logarithm of 1+x
math.log2() Returns the base-2 logarithm of x
math.perm() Returns the number of ways to choose k items from n items with order and without
repetition
math.pow() Returns the value of x to the power of y
math.prod() Returns the product of all the elements in an iterable
https://www.w3schools.com/python/module_math.asp

Math Methods
79
math.radians() Converts a degree value into radians
math.remainder() Returns the closest value that can make numerator
completely divisible by the denominator
math.sin() Returns the sine of a number
math.sinh() Returns the hyperbolic sine of a number
math.sqrt() Returns the square root of a number
math.tan() Returns the tangent of a number
math.tanh() Returns the hyperbolic tangent of a number
math.trunc() Returns the truncated integer parts of a number
Math Constants
Constant Description
math.e Returns Euler's number (2.7182...)
math.inf Returns a floating-point positive infinity
math.nan Returns a floating-point NaN (Not a Number) value
math.pi Returns PI (3.1415...)
math.tau Returns tau (6.2831...)

cmath Module
80
Method Description
cmath.acos(x) Returns the arc cosine value of x
cmath.acosh(x) Returns the hyperbolic arc cosine of x
cmath.asin(x) Returns the arc sine of x
cmath.asinh(x) Returns the hyperbolic arc sine of x
cmath.atan(x) Returns the arc tangent value of x
cmath.atanh(x) Returns the hyperbolic arctangent value of x
cmath.cos(x) Returns the cosine of x
cmath.cosh(x) Returns the hyperbolic cosine of x
cmath.exp(x) Returns the value of E
x
, where E is Euler's number (approximately
2.718281...), and x is the number passed to it
cmath.isclose() Checks whether two values are close, or not
cmath.isfinite(x) Checks whether x is a finite number
cmath.isinf(x) Check whether x is a positive or negative infinty
cmath.isnan(x) Checks whether x is NaN (not a number)
cmath.log(x[, base]) Returns the logarithm of x to the base
cmath.log10(x) Returns the base-10 logarithm of x

cmath Module
81
cmath.phase() Return the phase of a complex number
cmath.polar() Convert a complex number to polar coordinates
cmath.rect() Convert polar coordinates to rectangular form
cmath.sin(x) Returns the sine of x
cmath.sinh(x) Returns the hyperbolic sine of x
cmath.sqrt(x) Returns the square root of x
cmath.tan(x) Returns the tangent of x
cmath.tanh(x) Returns the hyperbolic tangent of x
cMath Constants
Constant Description
cmath.e Returns Euler's number (2.7182...)
cmath.inf Returns a floating-point positive infinity value
cmath.infj Returns a complex infinity value
cmath.nan Returns floating-point NaN (Not a Number) value
cmath.nanj Returns coplext NaN (Not a Number) value
cmath.pi Returns PI (3.1415...)
cmath.tau Returns tau (6.2831...)

Creating a Function -recap
82
• A function is a block of code which only runs when it is called.
• You can pass data, known as parameters, into a function.
• A function can return data as a result.
In Python a function is defined using the def keyword:
def my_function():
print("Hello from a function")
Calling a Function
my_function()

83
Arguments
• Information can be passed into functions as arguments.
• Arguments are specified after the function name, inside the parentheses.
• You can add as many arguments as you want, just separate them with a comma.
• The following example has a function with one argument (fname). When the function is called, we pass along a first
name, which is used inside the function to print the full name:
def my_function(fname):
print(fname + “ Keep doing")
my_function(“John")
my_function(“SAM")
my_function(“Raj")

84
Parameters or Arguments?
The terms parameter and argument can be used for the same thing: information that are passed into a function.
From a function's perspective:
A parameter is the variable listed inside the parentheses in the function definition.
An argument is the value that is sent to the function when it is called.
Number of Arguments
By default, a function must be called with the correct number of arguments. Meaning that if your function expects
2 arguments, you have to call the function with 2 arguments, not more, and not less.
If you try to call the function with 1 or 3 arguments, you will get an error:
def my_function(fname, lname):
print(fname + " " + lname)
my_function("Samuel", "Abhishek")

85
Arbitrary Arguments, *args
• If you do not know how many arguments that will be passed into your function, add a * before the parameter name in the
function definition.
• This way the function will receive a tuple of arguments, and can access the items accordingly:
def my_function(*kids):
print("The youngest child is " + kids[2])
my_function(“John", “SAM", “Raj")
Keyword Arguments
You can also send arguments with the key = value syntax.
This way the order of the arguments does not matter.
def my_function(child3, child2, child1):
print("The youngest child is " + child3)
my_function(child1 = “John", child2 = “SAM", child3 = “Raj")

86
Arbitrary Keyword Arguments, **kwargs
If you do not know how many keyword arguments that will be passed into your function, add two asterisk: ** before the parameter name
in the function definition.
This way the function will receive a dictionary of arguments, and can access the items accordingly:
def my_function(**kid):
print("His last name is " + kid["lname"])
my_function(fname = “John", lname = “Sam")
Default Parameter Value
The following example shows how to use a default parameter value.
If we call the function without argument, it uses the default value:
def my_function(country = "Norway"):
print("I am from " + country)
my_function("Sweden")
my_function("India")
my_function()
my_function("Brazil")

87
Passing a List as an Argument
You can send any data types of argument to a function (string, number, list, dictionary etc.), and it will be treated as
the same data type inside the function.
E.g. if you send a List as an argument, it will still be a List when it reaches the function:
def my_function(food):
for x in food:
print(x)
fruits = ["apple", "banana", "cherry"]
my_function(fruits)
Return Values
To let a function return a value, use the return statement:
def my_function(x):
return 5 * x
print(my_function(3))

88
The pass Statement
function definitions cannot be empty, but if you for some reason have a function definition with no content, put in the pass statement
to avoid getting an error.
def myfunction():
pass
Recursion
Python also accepts function recursion, which means a defined function can call itself.
Recursion is a common mathematical and programming concept. It means that a function calls itself.
This has the benefit of meaning that you can loop through data to reach a result.
The developer should be very careful with recursion as it can be quite easy to slip into writing a function
which never terminates, or one that uses excess amounts of memory or processor power. However,
when written correctly recursion can be a very efficient and mathematically-elegant approach to
programming.

89
def tri_recursion(k):
if(k > 0):
result = k + tri_recursion(k - 1)
print(result)
else:
result = 0
return result
print("nnRecursion Example Results")
tri_recursion(6)
In this example, tri_recursion() is a function that we have defined to call itself ("recurse").
We use the k variable as the data, which decrements (-1) every time we recurse.
The recursion ends when the condition is not greater than 0 (i.e. when it is 0).
To a new developer it can take some time to work out how exactly this works, best way to find out is by
testing and modifying it.

How to include pandas & numpy?
90
import numpy as np
import pandas as pd

Fuction.
def funName():
print("Hello from a function")
funName()
File Handling.
a = open(‘pantech.txt’, ‘r’)
print(a.read())
a.close()

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