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Programming in PythonTiji ThomasHODDepartment of Computer ApplicationsMACFAST

Jointly organized byDept. of Computer Applications, MACFASTKSCSTE&UNAI , Computer Society of India (CSI)MAR ATHANASIOS COLLEGE FOR ADVANCED STUDIES TIRUVALLA(MACFAST)UNAI-MACFAST-ASPIRETaliparamba Arts & Science CollegeAccredited 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 , MachineLearning , 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 Programa) Command Prompt• print “Hello World”• b)IDLE1. Run IDLE. ...2. Click File, New Window. ...3. Enter your script and save file with . Python files have afile 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 yourscript.

Reading Keyboard Input• Python provides two built-in functions to read a line of text fromstandard input, which by default comes from the keyboard. Thesefunctions are −• raw_input• input• The raw_input Function• The raw_input([prompt]) function reads one linefrom 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 toraw_input, except that it assumes the input is avalid Python expression and returns the evaluatedresult to you.str = input("Enter your input: ");print "Received input is : ", str

Python Decision MakingStatement Descriptionif statementsAn if statement consists of a boolean expressionfollowed by one or more statements.if...else statementsAn if statement can be followed by an optionalelse statement, which executes when the booleanexpression is FALSE.If .. elifYou can use one if or else if statement insideanother if or else if statement(s).

Indentation• Python provides no braces to indicate blocks ofcode for class and function definitions or flowcontrol. Blocks of code are denoted by lineindentationif True:print "True"else:print "False"

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

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

Example for#for loop examplestr= “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 withinsquare brackets ([]). To some extent, lists are similar to arrays in C.One difference between them is that all the items belonging to alist 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 list1. 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 usefulto generate sequences of numbers in the form of alist.• The given end point is never part of the generatedlist;

Basic list operationsLength - lenConcatenation : +Repetition - ['Hi!'] * 4Membership - 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 fruitsfruits.sort()for i in fruits:print iprint "nnnReverse ordernnn"fruits.sort(reverse=True)for i in fruits:print i

Python Tuples• A tuple consists of a number of values separated bycommas. Tuples are enclosed within parentheses.• The main differences between lists and tuples are:Lists are enclosed in brackets ( [ ] ) and theirelements and size can be changed, while tuples areenclosed in parentheses ( ( ) ) and cannot beupdated.• 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 inPerl and consist of key-value pairs• Dictionaries are enclosed by curly braces ({ }) andvalues can be assigned and accessed using squarebraces ([]).

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 followedby the function name and parentheses ( ( ) ).• Any input parameters or arguments should be placedwithin these parentheses.• The first statement of a function can be an optionalstatement - the documentation string of the function ordocstring..• The statement return [expression] exits a function,optionally passing back an expression to the caller. Areturn statement with no arguments is the same asreturn None.

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

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

Modes Descriptionr Read only. Starts at the beginning of the filer+ Read/Write. Starts at the beginning of the filew Write only. Opens and clears the contents of file; orcreates a new file if it doesn't existw+ Read/Write. Opens and clears the contents of file; orcreates a new file if it doesn't exista Append. Opens and writes to the end of the file or createsa new file if it doesn't exista+ Read/Append. Preserves file content by writing to the endof the file

• Opening and Closing Files• The open Functionfile object = open(file_name [, access_mode][, buffering])• file_name: The file_name argument is a string value thatcontains the name of the file that you want to access.• access_mode: The access_mode determines the mode inwhich the file has to be opened, i.e., read, write, append,etc.• The close() MethodThe close() method of a file object flushes any unwritteninformation and closes the file object, after which no morewriting can be done.

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

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

Regular Expression• Regular expressions are essentially a tiny, highlyspecialized programming language embeddedinside Python and made available through the remodule.

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

Various methods of Regular ExpressionsThe ‘re’ package provides multiple methods toperform queries on an input string. Here are themost commonly used methods1.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 thestringstr='MCA , MBA , BCA , BBA're.match('MCA' , str)re.match("MBA" , str)

re.search()search() method is able to find a pattern from anyposition of the string but it only returns the firstoccurrence of the search pattern.

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

Finding all Adverbsimport refile= 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 occurrencesof given pattern.import restr = '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 newsub string. If the pattern is not found, string isreturned unchanged.import restr = 'BCA BSc BCA'print strresult=re.sub(r"B", "M" , str)print "After replacement"print result

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

Project -1•Extract information from anExcel file using Python

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

Connection to a SQLite Databaseimport sqlite3conn = sqlite3.connect('example.db')Once you have a Connection, you can create aCursor object and call its execute() method toperform SQL commands:c = conn.cursor()

ProjectStudent Information System(SIS)Insert Data -> insertdata.pyUpdate Data -> updatedata.pyDelete Data ->deletedata.pyDisplay Students List ->list.py

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