Programming in Python

Programming in Python
Tiji Thomas
HOD
Department of Computer Applications
MACFAST

Jointly organized by
Dept. of Computer Applications, MACFAST
KSCSTE
&
UNAI , Computer Society of India (CSI)
MAR ATHANASIOS COLLEGE FOR ADVANCED STUDIES TIRUVALLA
(MACFAST)
UNAI-MACFAST-ASPIRE
Taliparamba Arts & Science College
Accredited by NAAC with A grade

Introduction
 Python is a general-purpose interpreted, object-
oriented, and high-level programming language.
 What can we do with Python –Web Development , ,
Desktop Applications, Data Science , Machine
Learning , Computer Games , NLP etc.
 Python supports many databases (SQLite, Sqlite,
Oracle, Sybase, PostgreSQL etc.)
 Python is an open source software
 Google, Instagram, YouTube , Quora etc

Executing a Python Program
a) Command Prompt
• print “Hello World”
• b)IDLE
1. Run IDLE. ...
2. Click File, New Window. ...
3. Enter your script and save file with . Python files have a
file extension of ".py"
4. Select Run, Run Module (or press F5) to run your script.
5. The "Python Shell" window will display the output of your
script.

Reading Keyboard Input
• Python provides two built-in functions to read a line of text from
standard input, which by default comes from the keyboard. These
functions are −
• raw_input
• input
• The raw_input Function
• The raw_input([prompt]) function reads one line
from standard input and returns it as a string
(removing the trailing newline).
str = raw_input("Enter your input: ");
print "Received input is : ", str

• The input Function
• The input([prompt]) function is equivalent to
raw_input, except that it assumes the input is a
valid Python expression and returns the evaluated
result to you.
str = input("Enter your input: ");
print "Received input is : ", str

Python Decision Making
Statement Description
if statements
An if statement consists of a boolean expression
followed by one or more statements.
if...else statements
An if statement can be followed by an optional
else statement, which executes when the boolean
expression is FALSE.
If .. elif
You can use one if or else if statement inside
another if or else if statement(s).

Indentation
• Python provides no braces to indicate blocks of
code for class and function definitions or flow
control. Blocks of code are denoted by line
indentation
if True:
print "True"
else:
print "False"

Python Loops
• while - loops through a block of code if and as long
as a specified condition is true
• for - loops through a block of code a specified
number of times

Example - while
#Display first n numbers
n=input("Enter value for n ")
i=1
while i<=n:
print i
i= i + 1

Example for
#for loop example
str= “Python”
for letter in str:
print 'Current Letter :', letter

Standard Data Types
• Python has five standard data types −
• Numbers
• String
• List
• Tuple
• Dictionary

Strings
• Set of characters represented in the quotation marks.
Python allows for either pairs of single or double quotes
• str = 'Hello World!'
• print str # Prints complete string
• print str[0] # Prints first character of the string
• print str[2:5] # Prints characters starting from 3rd to 5th
• print str[2:] # Prints string starting from 3rd character
• print str * 2 # Prints string two times
• print str + "TEST" # Prints concatenated string

Python Lists
• A list contains items separated by commas and enclosed within
square brackets ([]). To some extent, lists are similar to arrays in C.
One difference between them is that all the items belonging to a
list can be of different data type.
• list = [ 'abcd', 786 , 2.23, 'john', 70.2 ]
ls = [123, 'john']
• print list # Prints complete list
• print list[0] # Prints first element of the list
• print list[1:3] # Prints elements starting from 2nd till 3rd
• print list[2:] # Prints elements starting from 3rd element
• print ls * 2 # Prints list two times
• print list + ls # Prints concatenated lists

Python Lists
• Add elements to a list
1. mylist.append(10)
2. mylist.extend(["Raju",20,30])
3. mylist.insert(1,"Ammu")
• Search within lists -mylist.index('Anu’)
• Delete elements from a list - mylist.remove(20)

range function
• The built-in range function in Python is very useful
to generate sequences of numbers in the form of a
list.
• The given end point is never part of the generated
list;

Basic list operations
Length - len
Concatenation : +
Repetition - ['Hi!'] * 4
Membership - 3 in [1, 2, 3]
Iteration- for x in [1, 2, 3]: print x,

Sorting an array - list.sort()
fruits = ["lemon", "orange", "banana", "apple"]
print fruits
fruits.sort()
for i in fruits:
print i
print "nnnReverse ordernnn"
fruits.sort(reverse=True)
for i in fruits:
print i

Python Tuples
• A tuple consists of a number of values separated by
commas. Tuples are enclosed within parentheses.
• The main differences between lists and tuples are:
Lists are enclosed in brackets ( [ ] ) and their
elements and size can be changed, while tuples are
enclosed in parentheses ( ( ) ) and cannot be
updated.
• read-only lists

Tuple Example
• tuple = ( 'abcd', 786 , 2.23, 'john', 70.2 )
• tinytuple = (123, 'john')
• print tuple # Prints complete list
• print tuple[0] # Prints first element of the list
• print tuple[1:3] # Prints elements starting from 2nd till 3rd
• print tuple[2:] # Prints elements starting from 3rd element
• print tinytuple * 2 # Prints list two times
• print tuple + tinytuple # Prints concatenated lists

Operations on Tuple
• 1 Accessing Values in Tuples
• 2 Updating Tuples - not possible
• 3 Delete Tuple Elements - not possible
• 4 Create new tuple from existing tuples is possible
• Functions - cmp ,len , max , min

Python Dictionary
• Python's dictionaries are kind of hash table type.
They work like associative arrays or hashes found in
Perl and consist of key-value pairs
• Dictionaries are enclosed by curly braces ({ }) and
values can be assigned and accessed using square
braces ([]).

Example
• dict = {}
• dict['one'] = "This is one"
• dict[2] = "This is two"
• tinydict = {'name': 'john','code':6734, 'dept': 'sales'}
• print dict['one'] # Prints value for 'one' key
• print dict[2] # Prints value for 2 key
• print tinydict # Prints complete dictionary
• print tinydict.keys() # Prints all the keys
• print tinydict.values() # Prints all the values

Python Functions
• Function blocks begin with the keyword def followed
by the function name and parentheses ( ( ) ).
• Any input parameters or arguments should be placed
within these parentheses.
• The first statement of a function can be an optional
statement - the documentation string of the function or
docstring.
.
• The statement return [expression] exits a function,
optionally passing back an expression to the caller. A
return statement with no arguments is the same as
return None.

Example -1
Function for find maximum of two numbers
Example -2
Function for Read and Display list
Example -3
Function for search in a list
Example -4
Function for prime numbers

Opening a File
• The open() function is used to open files in Python.
• The first parameter of this function contains the
name of the file to be opened and the second
parameter specifies in which mode the file should
be opened
Example
• File=open(“macfast.txt” , “w”)

Modes Description
r Read only. Starts at the beginning of the file
r+ Read/Write. Starts at the beginning of the file
w Write only. Opens and clears the contents of file; or
creates a new file if it doesn't exist
w+ Read/Write. Opens and clears the contents of file; or
creates a new file if it doesn't exist
a Append. Opens and writes to the end of the file or creates
a new file if it doesn't exist
a+ Read/Append. Preserves file content by writing to the end
of the file

• Opening and Closing Files
• The open Function
file object = open(file_name [, access_mode][, buffering])
• file_name: The file_name argument is a string value that
contains the name of the file that you want to access.
• access_mode: The access_mode determines the mode in
which the file has to be opened, i.e., read, write, append,
etc.
• The close() Method
The close() method of a file object flushes any unwritten
information and closes the file object, after which no more
writing can be done.

• The write() Method
• The write() method writes any string to an open file
• The write() method does not add a newline
character ('n') to the end of the string −
# Open a file
file = open(“test.txt", "wb")
file.write( “ Two day workshop on Python ");
# Close opend file
File.close()

• The read() Method
• The read() method reads a string from an open file.
f= open(“test.txt", "r")
str = f.read();
print str
fo.close()

Regular Expression
• Regular expressions are essentially a tiny, highly
specialized programming language embedded
inside Python and made available through the re
module.

• Regular expressions are useful in a wide variety of
text processing tasks, and more generally string
processing
• Data validation
• Data scraping (especially web scraping),
• Data wrangling,
• Parsing,
• Syntax highlighting systems

Various methods of Regular Expressions
The ‘re’ package provides multiple methods to
perform queries on an input string. Here are the
most commonly used methods
1.re.match()
2.re.search()
3.re.findall()
4.re.split()
5.re.sub()

re.match()
This method finds match if it occurs at start of the
string
str='MCA , MBA , BCA , BBA'
re.match('MCA' , str)
re.match("MBA" , str)

re.search()
search() method is able to find a pattern from any
position of the string but it only returns the first
occurrence of the search pattern.

Re.findall
• findall helps to get a list of all matching patterns
import re
str='MCA , MBA , BCA , BBA , MSC'
result =re.findall (r"Mww" , str)
if result:
for i in result:
print i
else:
print "Not Found"

Finding all Adverbs
import re
file= open(‘story.txt' , "r")
str=file.read();
result=re.findall(r"w+ly",str)
for i in result:
print i

re.split()
This methods helps to split string by the occurrences
of given pattern.
import re
str = 'MCA MBA BCA MSC BBA BSc'
result=re.split(" ",str)
for i in result:
print i

re.sub(pattern, repl, string)
• It helps to search a pattern and replace with a new
sub string. If the pattern is not found, string is
returned unchanged.
import re
str = 'BCA BSc BCA'
print str
result=re.sub(r"B", "M" , str)
print "After replacement"
print result

Change gmail.com to macfast.org
using re.sub()
import re
str = "tiji@gmail.com ,anju@gmail.com ,anu@gmail.com"
print str
newstr= re.sub(r"@w+.com" , "@macfast.org" , str)
print "Change gmail.com to macfast.org "
print newstr

Project -1
•Extract information from an
Excel file using Python

What is SQLite?
SQLite is an embedded SQL database engine
•SQLite is ideal for both small and large
applications
•SQLite supports standard SQL
•Open source software

Connection to a SQLite Database
import sqlite3
conn = sqlite3.connect('example.db')
Once you have a Connection, you can create a
Cursor object and call its execute() method to
perform SQL commands:
c = conn.cursor()

Project
Student Information System(SIS)
Insert Data -> insertdata.py
Update Data -> updatedata.py
Delete Data ->deletedata.py
Display Students List ->list.py

Programming in Python

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