CBSE CLASS XI CHAPTER 5: GETTING STARTED WITH PYTHON

CBSE CLASS XI CHAPTER 5: GETTING STARTED WITH PYTHON - SOLVED 

Summary

• Python is an open-source, high level, interpreter based language that can be used for a multitude of scientific and non-scientific computing purposes.

• Comments are non-executable statements in a program.

• An identifier is a user defined name given to a variable or a constant in a program.

• The process of identifying and removing errors from a computer program is called debugging.

• Trying to use a variable that has not been assigned a value gives an error.

• There are several data types in Python — integer, boolean, float, complex, string, list, tuple, sets, None and dictionary.

Exercise

1. Which of the following identifier names are invalid and why?

i Serial_no.                     v Total_Marks

ii 1st_Room                  vi total-Marks

iii Hundred$                 vii _Percentage

iv Total Marks              viii True

Answer: Invalid identifiers are: 1st_Room, Hundred$, Total Marks and True.

Reason: 1st_Room: identifier name cannot start with a digit

Hundred$: Cannot use special character '$'

Total Marks: space is not allowed between two words

True: it is a keyword

2. Write the corresponding Python assignment statements:

a) Assign 10 to variable length and 20 to variable breadth.

length = 10

breadth = 20

b) Assign the average of values of variables length and breadth to a variable sum.

sum = (length+breadth)/2

c) Assign a list containing strings ‘Paper’, ‘Gel Pen’, and ‘Eraser’ to a variable stationery.

stationary = ["Paper","Gel Pen","Eraser"]

d) Assign the strings ‘Mohandas’, ‘Karamchand’, and ‘Gandhi’ to variables first, middle and last.

first = 'Mohandas'

second = 'Karamchand'

third = 'Gandhi'

e) Assign the concatenated value of string variables first, middle and last to variable fullname. Make sure to incorporate blank spaces appropriately between different parts of names.

fullname =first+' '+second+' '+third

3. Write logical expressions corresponding to the following statements in Python and evaluate the expressions (assuming variables num1, num2, num3,first, middle, last are already having meaningful values):

a) The sum of 20 and –10 is less than 12.

num1 = 10

num2 = -20

num3 = 12

print(num1 + num2 < num3)

b) num3 is not more than 24.

print(num3 < 24)

c) 6.75 is between the values of integers num1 and num2.

print(num1 < 6.75 and 6.75 < num2)

d) The string ‘middle’ is larger than the string ‘first’ and smaller than the string ‘last’.

print( middle > first and middle < last)

e) List Stationery is empty.

4. Add a pair of parentheses to each expression so that it evaluates to True.

a) 0 == 1 == 2    

(0 == (1 == 2))

b) 2 + 3 == 4 + 5 == 7

2 + (3 == 4) + 5 == 7

c) 1 < -1 == 3 > 4

(1 < -1) == (3 > 4)

5. Write the output of the following: a) num1 = 4 num2 = num1 + 1 num1 = 2 print (num1, num2)

2 5 b) num1, num2 = 2, 6 num1, num2 = num2, num1 + 2 print (num1, num2)

6 4 c) num1, num2 = 2, 3 num3, num2 = num1, num3 + 1 print (num1, num2, num3)

2 13 2

6. Which data type will be used to represent the following data values and why? a) Number of months in a year - int - always takes integral value b) Resident of Delhi or not - bool - binary c) Mobile number - int - always takes integral value d) Pocket money - float - e) Volume of a sphere - float f) Perimeter of a square - float g) Name of the student - str h) Address of the student - str

7. Give the output of the following when num1 = 4, num2 = 3, num3 = 2 a) num1 += num2 + num3 print (num1)

9 b) num1 = num1 ** (num2 + num3) print (num1)

1024 c) num1 **= num2 + num3

1024 d) num1 = '5' + '5' print(num1)

55

e) print(4.00/(2.0+2.0))

1.0 f) num1 = 2+9*((3*12)-8)/10 print(num1)

27.2 g) num1 = 24 // 4 // 2 print(num1)

3 h) num1 = float(10) print (num1)

10.0 i) num1 = int('3.14') print (num1)

3 j) print('Bye' == 'BYE')

False k) print(10 != 9 and 20 >= 20)

True l) print(10 + 6 * 2 ** 2 != 9//4 -3 and 29 >= 29/9)

True m) print(5 % 10 + 10 < 50 and 29 <= 29)

True n) print((0 < 6) or (not(10 == 6) and (10<0)))

True

8. Categorise the following as syntax error, logical error or runtime error: a) 25 / 0 runtime error b) num1 = 25; num2 = 0; num1/num2 logical error

9. A dartboard of radius 10 units and the wall it is hanging on are represented using a two-dimensional coordinate system, with the board’s center at coordinate (0,0). Variables x and y store the x-coordinate and the y-coordinate of a dart that hits the dartboard. Write a Python expression using variables x and y that evaluates to True if the dart hits (is within) the dartboard, and then evaluate the expression for these dart coordinates: a) (0,0) b) (10,10) c) (6, 6) d) (7,8)

Expression: (x**2+y**2)**(1/2) <= 10

PYTHON CODE

x = float(input("Enter the x co-ordinate:"))

y = float(input("Enter the y co-ordinate:"))

d = (x**2+y**2)**(1/2) # distance of the point from the origin

if (d <= 10):

    print("The dart hits the board.")

10. Write a Python program to convert temperature in degree Celsius to degree Fahrenheit. If water boils at 100 degree C and freezes as 0 degree C, use the program to find out what is the boiling point and freezing point of water on the Fahrenheit scale. (Hint: T(°F) = T(°C) × 9/5 + 32)                                                                                        

degreeCelsius = float(input("Enter the temperature in Celsius:"))

degreeFahrenheit = (degreeCelsius*9)/5 +32

print("Corresponding value in Fahrenheit is", degreeFahrenheit)

freezingTemp = (0*9)/5 +32

print("Water freezes at", freezingTemp," degree F")

boilingTemp = (100*9)/5 +32

print("Water boils at", boilingTemp," degree F")

11. Write a Python program to calculate the amount payable if money has been lent on simple interest.

Principal or money lent = P, Rate of interest = R% per annum and Time = T years. Then Simple Interest (SI) = (P x R x T)/ 100. Amount payable = Principal + SI. P, R and T are given as input to the program.

principal = float(input("Enter the principal or money lent:"))

rateOfInterest = float(input("Enter the rate of interest p.a:"))

time = float(input("Enter the time in years:"))

simpleInterest = (principal*rateOfInterest*time)/100

amount = principal + simpleInterest

print("Amount after %.1f years is %.2f" %(time,amount))

12. Write a program to calculate in how many days a work will be completed by three persons A, B and C together. A, B, C take x days, y days and z days respectively to do the job alone. The formula to calculate the number of days if they work together is xyz/(xy + yz + xz) days where x, y, and z are given as input to the program.

x = float(input("Number of days taken by A to complete the work:"))

y = float(input("Number of days taken by B to complete the work:"))

z = float(input("Number of days taken by C to complete the work:"))

timeRequiredWorkingTogether = (x*y*z)/(x*y+y*z+z*x)

print("Time required working together =",timeRequiredWorkingTogether)

13. Write a program to enter two integers and perform all arithmetic operations on them.

x = float(input("Enter the first number:"))

y = float(input("Enter the second number:"))

print("Sum",x+y)

print("Difference (x-y)",x+y)

print("Product",x*y)

if y != 0:

    print("Division (x/y)",x/y)

elif x != 0:

    print("Division (y/x)",y/x)

else:

    print("Cannot Divide")

if x!= 0 and y!=0:

    print("Power (x to the power y",x**y)

if  x > 0 and x!=1 and y>0:

    print ("Logarithm base x of y is : ", end="")

    print (math.log(y,x))

else:

    print ("Logarithm base x of y is not defined:") 

14. Write a program to swap two numbers using a third variable.

firstVariable= input("Enter the first variable(x):")

secondVariable = input("Enter the second variable(y):")

print("Before Swapping")

print("The first variable is(x)=",firstVariable)

print("The second variable is(y)=",secondVariable)

#swapping

thirdVariable = firstVariable

firstVariable = secondVariable

secondVariable = thirdVariable

print("After Swapping")

print("The first variable is(x)=",firstVariable)

print("The second variable is(y)=",secondVariable)

15. Write a program to swap two numbers without using a third variable.

firstVariable= int(input("Enter the first variable(x):"))

secondVariable = int(input("Enter the second variable(y):"))

print("Before Swapping")

print("The first variable is(x)=",firstVariable)

print("The second variable is(y)=",secondVariable)

#swapping 

firstVariable = firstVariable + secondVariable

secondVariable = firstVariable - secondVariable

firstVariable = firstVariable - secondVariable

print("After Swapping")

print("The first variable is(x)=",firstVariable)

print("The second variable is(y)=",secondVariable)

16. Write a program to repeat the string ‘‘GOOD MORNING” n times.

n = int(input("Enter the value of n:"))

messageDisplay = "GOOD MORNING"

for i in range(n):

    print(messageDisplay)

                 

if users enter values different from positive integers:                                                                     

try:

    n = int(input("Enter the value of n:"))

    messageDisplay = "GOOD MORNING"

    if n <= 0:

        print("Enter a positive integer:")

    for i in range(n):

        print(messageDisplay)

except ValueError as e:

    print("You must enter an integer:")

                         

17. Write a program to find average of three numbers.

numbOne =float(input("Enter the first number:"))

numbTwo =float(input("Enter the second number:"))

numbThree =float(input("Enter the third number:"))

average = (numbOne+numbTwo+numbThree)/3

print("Average of the numbers is", average)

# Program for finding average on N numbers

numberList = []

N = int(input("How many numbers?"))

for i in range(N):

    print("Enter the number at position",i+1,":",end="")

    numberList.append(float(input()))

sumOfNumbers = 0

for i in range(N):

    sumOfNumbers += numberList[i]

print("Average of the numbers is", sumOfNumbers/N)

18. The volume of a sphere with radius r is 4/3πr³. Write a Python program to find the volume of spheres with radius 7cm, 12cm, 16cm, respectively.

import math

radius =float(input("Enter the radius of the sphere:"))

volumeOfSphere = (4*math.pi*radius**3)/3

print("Volume of the sphere is:",round(volumeOfSphere,3))

Using functions:

import math

def VolumeOfSphere(radius):

    volumeOfSphere = (4*math.pi*radius**3)/3

    print("Volume of the sphere with radius",radius," cm is:",round(volumeOfSphere,3))

radius =float(input("Enter the radius of the sphere:"))

VolumeOfSphere(radius)

VolumeOfSphere(7)

VolumeOfSphere(12)

VolumeOfSphere(16)

19. Write a program that asks the user to enter their name and age. Print a message addressed to the user that tells the user the year in which they will turn 100 years old.

nameOfUser =str(input("Enter your name:"))

currentYear = int(input("Enter the current year:"))

print("Enter your age as of",currentYear,end=":")

ageOfUser = int(input())

if ageOfUser == 100:

    print("Congratulations!", nameOfUser,"you have reached a milestone")

else:

    while ageOfUser < 100:

        ageOfUser +=1

        currentYear +=1

    print(nameOfUser,"you will turn 100 in the year",currentYear,"!")

20. The formula E = mc² states that the equivalent energy (E) can be calculated as the mass (m) multiplied by the speed of light (c = about 3×10⁸ m/s) squared.

Write a program that accepts the mass of an object and determines its energy.

massOfObject = float(input("Enter the mass in kg:"))

energyEquivalentToMass = massOfObject*(3*10**8)**2

print("Energy of the object is %10.2E" %(energyEquivalentToMass),"J")

21. Presume that a ladder is put upright against a wall. Let variables length and angle store the length of the ladder and the angle that it forms with the ground as it leans against the wall. Write a Python program to compute the height reached by the ladder on the wall for the following values of length and angle: a) 16 feet and 75 degrees b) 20 feet and 0 degrees c) 24 feet and 45 degrees d) 24 feet and 80 degrees

import math

def heightReachedByLadder(angle,lengthOfLadder):

    print("Height reached by the ladder on the wall",round(lengthOfLadder*math.sin(angle),3),"m")

lengthOfLadder = float(input("Enter the length of the ladder in meters:"))

angle = float(input("Enter the angle amde by the ladder with the horizontal in degrees:"))

#converting to radian then using the value

heightReachedByLadder((angle*math.pi)/180,lengthOfLadder)

Case Study-based Question Schools use “Student Management Information System” (SMIS) to manage student-related data. This system provides facilities for: • recording and maintaining personal details of students. • maintaining marks scored in assessments and computing results of students. • keeping track of student attendance. • managing many other student-related data.

Let us automate this process step by step. Identify the personal details of students from your school identity card and write a program to accept these details for all students of your school and display them in the following format.

numberOfStudents = int(input("Enter the total number of students in the school:"))

recordList = []

schoolName = "The CPROJECTT"

for i in range(numberOfStudents):

    recordList.append(str(input("Enter the name of the student:")))

    recordList.append(str(input("Enter the roll number of the student:")))

    recordList.append(str(input("Enter the class of the student(Roman numerals):")))

    recordList.append(str(input("Enter the section of the student(A/B/C/D):")))

    recordList.append(str(input("Enter the address of the student:")))

    recordList.append(str(input("Enter the city name:")))

    recordList.append(str(input("Enter the pin code:")))

    recordList.append(str(input("Enter the Parent's/Guardian's contact number:")))

print()

for i in range(numberOfStudents):

    print("Name of School",schoolName)

    print("Student Name:",recordList[i+0],end ="        ")

    print("Roll No:",recordList[i+1])    

    print("Class:",recordList[i+2],end ="       ")

    print("Section:",recordList[i+3])

    print("Address:",recordList[i+4])

    print("City:",recordList[i+5],end ="        ")

    print("Pincode:",recordList[i+6])

    print("Parent's/Guardian Contact Number:",recordList[i+7])