Mr Nuwan KodagodaHead/Department of Information TechnologySri Lanka Institute of Information Technology

GCE (A/L) ICT Training for Teachers (Last Updated on 21st March 2011)

OutcomesIntroduction to PythonData Types and CalculationsSelectionRepetitionString HandlingFunctionsListsFile HandlingClasses

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Programming Languages

Programming LanguagesThere are hundreds of programming languages.Very broadly these languages are categorized as Low Level LanguagesHigh Level Languages

Low Level LanguagesMore closer to the Architecture of the computer.Very difficult for us humans to use.

Memory AddressesMachine CodeAssembly

High Level LanguagesHigh Level Languages are closer to human languages.

Dim radius as integerDim area as integer

radius = txtRadius.textarea = 22/7*radius*radiusmsgbox area

How a Computer Program worksThe Program you write is executed by the CPU.

Since the CPU can only understand machine code your program needs to be converted into machine code.

How a Computer Program worksDim radius as integerDim area as integer

radius = txtRadius.textarea = 22/7*radius*radiusmsgbox areaC8B723A7D7AA89DD89D23A9F4A9...Source CodeMachine Code

How a Computer Program worksThe software that does the conversion to machine code comes in two flavours.

CompilersInterpreters

What is a Compiler?A compiler converts your entire program to machine code at one go.

After compilation you have an executable file.

e.g. an EXE, COM file for PCs

How an Interpreter WorksAn Interpreter converts your program to machine code one instruction at a time.

PythonPython is an easy to learn, powerful programming language. It has efficient high-level data structures and a simple but effective approach to object-oriented programming. Python is an ideal language for scripting and rapid application development in many areas on most platforms.GCE (A/L) ICT Training for Teachers

Python LanguageNo variable, data type declaration necessary (Dynamically Typed)Case Sensitive variablesIndentation of 4 characters used for block structures (e.g. if, while, functions)Program extension is .pyRuns on multiple platformsOpen SourceGCE (A/L) ICT Training for Teachers

Python KeywordsLike most modern languages Python has only a few keywords.GCE (A/L) ICT Training for Teachers

HistoryDeveloped in the early 1990s by Guido van Rossum.The name Python was based a popular TV show called the Monty Python.

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Which version of Python should I use?There are two versions of Python availablePython 2 the latest is 2.71Python 3 the latest is 3.2For the ICT exam use Python 2Some differences e.g. in Python 3 the print is a function so print 10, 20 has to be written as print(10,20)GCE (A/L) ICT Training for Teachers

Downloading Python and InstallingGCE (A/L) ICT Training for Teachers

Operator PrecedenceGCE (A/L) ICT Training for Teachers

OperatorDescriptionAssociatively* / %Multiplication/division/modulusleft-to-right+ -Addition/subtractionleft-to-right

Arithmetic OperatorsGCE (A/L) ICT Training for Teachers

(Python 3 only)

MCQ Question 41r=11; y=2.5; c=4 have been assigned to three variablesFind the value of r%3*c+10/y

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MCQ Question 41r=11; y=2.5; c=4 have been assigned to three variablesFind the value of r%3*c+10/y11%3*4+10/2.52*4+10/2.58+10/2.58+4.012.0

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Numerical Calculations10+20/2(10+20)/2

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Printing values in Pythonprint 10, Nadun, 1990

In Python 3 print is a function

print(10, Nadun, 1990)GCE (A/L) ICT Training for Teachers

Input Data in Python 2no1 = int(input(Enter an int Number : ))no2 = float(input(Enter a float Number : ))str = raw_input(Enter a string : )

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CalculationsWrite a python program to input a length in mm and convert it to inches.25.4 mm = 1 inchGCE (A/L) ICT Training for Teachers

inches.py

CalculationsWrite a python program to input a temperature in Celcius and convert it to Fahrenheit.

fahrenheit = 9/5* celcius +32GCE (A/L) ICT Training for Teachers

celcius.py

SelectionGCE (A/L) ICT Training for Teachers

if (cond) then Statement A else Statement B endif

SelectionGCE (A/L) ICT Training for Teachers

if (cond) then Statement A else Statement B endifif cond: Statement A else: Statement B

if statementWrite a program to input a mark and display Pass if it is greater than or equal to 50. Otherwise display Fail.GCE (A/L) ICT Training for Teachers

if statementWrite a program to input a number. Display if it is an even or an odd number.GCE (A/L) ICT Training for Teachers

oddeven.py

Nested if statementGCE (A/L) ICT Training for Teachers

if (test1) then block1else if (test2) then block2 else elseBlock endifendif

Nested if statementGCE (A/L) ICT Training for Teachers

if (test1) then block1else if (test2) then block2 else elseBlock endifendif if test1: block1elif test2: block2else: elseBlock

Nested If StatementGCE (A/L) ICT Training for Teachers

GradesWrite a program to input the marks of a student and calculate the grades.> 75 A65 to 75 B55 to 64 C45 to 54 S< 45 - W

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Nested If StatementWrite a program to input an amount and to calculate the discount as follows.Discounts>1000 - discount 10%500-1000 - discount 5%< 500 - discount 2%GCE (A/L) ICT Training for Teachers

MCQ Question 42What would be the output of this program.GCE (A/L) ICT Training for Teachers

MCQ Question 42If 10

Repetitiondo while (cond) execute Statement end whileGCE (A/L) ICT Training for Teachers

Repetitiondo while (cond) execute Statement end whileGCE (A/L) ICT Training for Teachers

while cond: execute Statement

whileWrite a program to Print numbers 1 to 9

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while1.py

whileWrite a program to Print numbers 1,3,5,7,9

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while2.py

whileWrite a program to print the tables of 7.GCE (A/L) ICT Training for Teachers

Using For loop in PythonRange command generates a list.A list is similar to an array, but it can store data of different types. It also could contain another list.range(1,10) produces the list[1,2,3,4,5,6,7,8,9]

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for r in range(1,10): print(r)

Using For loop in Pythonrange(1,10,2) produces the list[1,3,5,7,9]

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for r in range(1,10,2): print(r)

Using For loop in PythonAny list can be printed in the same wayMylist = [Java,C#, VB6, VB.NET,Python]

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for r in Mylist: print(r)JavaC#VB6VB.NETPython

Using For loop in PythonThis works the same for a stringcountry = SRI LANKA

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for r in country: print(r)SRI

LANKA

MCQ Question 43 What would be the output ?GCE (A/L) ICT Training for Teachers

MCQ Question 43 What would be the output ?r= 5s=3r = r+sr = 5+3 = 8s = r+3=8+3print 11r

MCQ Question 43 What would be the output ?r=8s=11r = r+sr = 8+11 = 19s = r+3=19+3=22print 22r

MCQ Question 43 What would be the output ?r=19s=22r = r+sr = 19+22 = 41s = r+3=41+3=44print 44r

MCQ Question 44 GCE (A/L) ICT Training for Teachers

Select the correct pseudo code for the given flow chart

MCQ Question 45Which of the above statements are correctGCE (A/L) ICT Training for Teachers

String Manipulationmystr = Sri Lankalen(mystr)mystr.upper() # upper casemystr.upper() # lower casemystr[0] # Smystr[-1] # a

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List Manipulationmylist = [10, Ajith, 67.3, 78.2]mylist[0] # 10mylist[3] # 78.2mylist[-1] # 78.2mylist[-2] # 67.3sublist = mylist[1:3] # [Ajith, 67.3]sublist = mylist[1:] # [Ajith, 67.3, 78.2]

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List Manipulationlen(mylist) #4mylist.append(89) # adds 89# [10, Ajith, 67.3, 78.2, 89]mylist.sort() # sorts listmylist.reverse() # reverses listGCE (A/L) ICT Training for Teachers

Break and ContinueA break statement inside a block will cause it to exit the loopA continue statement inside a block will skip the remaining instructions and go to the beginning of the loop.GCE (A/L) ICT Training for Teachers

Question II 3GCE (A/L) ICT Training for Teachers

python

AQ3c.py

Question II 3GCE (A/L) ICT Training for Teachers

pythonprogramming (one letter per line)

AQ3d.py

Part B Question 51 Cat 32 Dog 33 Rat 3GCE (A/L) ICT Training for Teachers

BQ5b.py

FunctionsA function that returns a value or does a particular task

def cube(x): return x*x*x

cube(10)GCE (A/L) ICT Training for Teachers

FunctionsWrite a function that converts mm to inches

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ExampleWrite a python program that returns the maximum of two numbersmax(10,30) # should return 30GCE (A/L) ICT Training for Teachers

Importing modules and functionsAssume there is a program called pythonprg.py which has two functions named func1() and func2()To use these functions from another python program we need to do the following.

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import pythonprgpythonprg.func1(3)

from pythonprg import func1,func2func1(3)

Setting PYTHONPATHStartCMDSET PYTHONPATH= c:\python27;c:\python27\programs

Importing modules from IDLEimport syssys.path.append(c:\\python27\\programs)

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Part B Question 55 x 1 = 55 x 2 = 105 x 3 = 155 x 4 = 205 x 5 = 255 x 6 = 305 x 7 = 355 x 8 = 405 x 9 = 455 x 10 = 505 x 11 = 55GCE (A/L) ICT Training for Teachers

BQ5b2.py

Question II 3GCE (A/L) ICT Training for Teachers

Pseudo Code for above flow chart# Pseudo code# x = 1# total = 0# do while (x 50) then# display "Good"# else# display "Bad"# endifGCE (A/L) ICT Training for Teachers

Python Codex = 1total = 0while x 50: print "Good"else: print "Bad"GCE (A/L) ICT Training for Teachers

File HandlingPython allows you to easily read and write data filesGCE (A/L) ICT Training for Teachers

Write data to a fileWrite a sample program to store data to a data file where commas separate values.

datafile = open ("marks.dat","w")datafile.write()GCE (A/L) ICT Training for Teachers

Read data from a fileWrite a sample program to read data from a data file where commas separate values.datafile = open ("marks.dat","r")record = datafile.readline()# split the data into a list for easier manipulation. The comma is the seperatormylist = record.strip(\n).split(,)GCE (A/L) ICT Training for Teachers

Part B Question 5GCE (A/L) ICT Training for Teachers

BQ5c.py

Object Oriented ProgramPython Supports OO just like any other modern programming languagePython code as usual is minimilisticBoth methods and attributes can be accessed from outside.GCE (A/L) ICT Training for Teachers

Classes and ObjectsA person workingIn a companyPerson

EmpNoNameAddressBasicSalOtHrsOtRate

CalcOtAmtCalcNetSalPropertiesMethods

Classes and ObjectsYou describe the objects details in a Class. A class is a blue print of an object.

Blue PrintHouse3House2House1

Classes# Shape.pyclass Rectangle: def __init__(self,x,y): def display(self): GCE (A/L) ICT Training for Teachers

import Shaperec1 = Shape.Rectangle(10,20)rec1.display()

Classes# Shape.pyclass Rectangle: def __init__(self,x,y): def display(self): GCE (A/L) ICT Training for Teachers

from Shape import Rectanglerec1 = Rectangle(10,20)rec1.display()

CircleWrite a class to represent a circleCalculate the area pi*r^2Calculate the perimeter 2*pi*rGCE (A/L) ICT Training for Teachers

MCQ 50GCE (A/L) ICT Training for Teachers

MCQ 50GCE (A/L) ICT Training for Teachers

MCQ 49GCE (A/L) ICT Training for Teachers

ExercisesWrite a program to input a series of numbers terminated by -999. Calculate and print the sum of the numbers entered.GCE (A/L) ICT Training for Teachers

ExerciseWrite a program to input the sum of 10 numbers.Modify the above program using a break statement so that when the number -999 is entered it will stop the entering of marksModify the above program to ignore negative numbers (except for -999). Use the continue statementGCE (A/L) ICT Training for Teachers