Flow of Control

Question 1

The if statement forms the selection construct in Python.

Question 2

The pass statement is a do nothing statement in Python.

Question 3

The for and while statements form the repetition construct in Python.

Question 4

Three constructs that govern the flow of control are sequence, selection/decision and repetition/iteration.

Question 5

In Python, indentation defines a block of statements.

Question 6

An if-else statement has less number of conditional checks than two successive ifs.

Question 7

The in operator tests if a given value is contained in a sequence or not.

Question 8

The two membership operators are in and not in.

Question 9

An iteration refers to one repetition of a loop.

Question 10

The for loop iterates over a sequence.

Question 11

The while loop tests a condition before executing the body-of-the-loop.

Question 12

The else clause can occur with an if as well as with loops.

Question 13

The else block of a loop gets executed when a loop ends normally.

Question 14

The else block of a loop will not get executed if a break statement has terminated the loop.

Question 15

The break statement terminates the execution of the whole loop.

Question 16

The continue statement terminates only a single iteration of the loop.

Question 17

The break and continue statements, together are called jump statements.

Question 18

In a nested loop, a break statement inside the inner loop, will terminate the inner loop only.

Question 1

In a Python program, a control structure:

1. directs the order of execution of the statements in the program ✓
2. dictates what happens before the program starts and after it terminates
3. defines program-specific data structures
4. manages the input and output of control characters

Question 2

An empty/null statement in Python is

1. go
2. pass ✓
3. over
4. ;

Question 3

The order of statement execution in the form of top to bottom, is known as .......... construct.

1. selection
2. repetition
3. sequence ✓
4. flow

Question 4

The .......... construct allows to choose statements to be executed, depending upon the result of a condition.

1. selection ✓
2. repetition
3. sequence
4. flow

Question 5

The .......... construct repeats a set of statements a specified number of times or as long as a condition is true.

1. selection
2. repetition ✓
3. sequence
4. flow

Question 6

Which of the following statements will make a selection construct?

1. if ✓
2. if-else ✓
3. for
4. while

Question 7

Which of the following statements will make a repetition construct?

1. if
2. if-else
3. for ✓
4. while ✓

Question 8

In Python, which of the following will create a block in a compound statement ?

1. colon
2. statements indented at a lower, same level ✓
3. indentation in any form
4. { }

Question 9

What signifies the end of a statement block or suite in Python ?

1. A comment
2. }
3. end
4. A line that is indented less than the previous line ✓

Question 10

Which one of the following if statements will not execute successfully ?

1. if (1, 2) :
       print('foo')
2. if (1, 2)
       print('foo') ✓
3. if (1, 2) :
   print('foo') ✓
4. if (1) :
       print( 'foo' )

Question 11

What does the following Python program display ?

x = 3                                
if x == 0:                          
    print ("Am I here?", end = ' ')   
elif x == 3:                         
    print("Or here?", end = ' ')
else :                               
    pass                             
print ("Or over here?")

1. Am I here?
2. Or here?
3. Am I here? Or here?
4. Or here? Or over here? ✓
5. Am I here? Or over here?

Question 12

If the user inputs : 2<ENTER>, what does the following code snippet print?

x = float(input())
if(x==1):
    print("Yes")
elif (x >= 2):
    print("Maybe")
else:
    print ("No")

1. Yes
2. No
3. Maybe ✓
4. Nothing is printed
5. Error

Question 13

Consider the following code segment:

a = int(input("Enter an integer: "))
b = int(input("Enter an integer: "))
if a <= 0:
   b = b +1
else:
   a = a + 1
if a > 0 and b > 0: 
   print ("W") 
elif a > 0:
   print("X") 
if b > 0:
   print("Y") 
else:
   print("Z")

What letters will be printed if the user enters 0 for a and 0 for b ?

1. Only W
2. Only X
3. Only Y ✓
4. W and X
5. W, X and Y

Question 14

Consider the following code segment:

a = int(input("Enter an integer: "))
b = int(input("Enter an integer: "))
if a <= 0:
   b = b +1
else:
   a = a + 1
if a > 0 and b > 0: 
   print ("W") 
elif a > 0:
   print("X") 
if b > 0:
   print("Y") 
else:
   print("Z")

What letters will be printed if the user enters 1 for a and 1 for b ?

1. W and X
2. W and Y ✓
3. X and Y
4. X and Z
5. W, X and Y

Question 15

Consider the following code segment:

a = int(input("Enter an integer: "))
b = int(input("Enter an integer: "))
if a <= 0:
   b = b +1
else:
   a = a + 1
if a > 0 and b > 0: 
   print ("W") 
elif a > 0:
   print("X") 
if b > 0:
   print("Y") 
else:
   print("Z")

What letters will be printed if the user enters 1 for a and -1 for b?

1. W and X
2. X and Y
3. Y and Z
4. X and Z ✓
5. W and Z

Question 16

Consider the following code segment:

a = int(input("Enter an integer: "))
b = int(input("Enter an integer: "))
if a <= 0:
   b = b +1
else:
   a = a + 1
if a > 0 and b > 0: 
   print ("W") 
elif a > 0:
   print("X") 
if b > 0:
   print("Y") 
else:
   print("Z")

What letters will be printed if the user enters 1 for a and 0 for b ?

1. W and X
2. X and Y
3. Y and Z
4. X and Z ✓
5. W and Z

Question 17

Consider the following code segment:

a = int(input("Enter an integer: "))
b = int(input("Enter an integer: "))
if a <= 0:
   b = b +1
else:
   a = a + 1
if a > 0 and b > 0: 
   print ("W") 
elif a > 0:
   print("X") 
if b > 0:
   print("Y") 
else:
   print("Z")

What letters will be printed if the user enters -1 for a and -1 for b?

1. Only W
2. Only X
3. Only Y
4. Only Z ✓
5. No letters are printed

Question 18

What values are generated when the function range(6, 0, -2) is executed ?

1. [4, 2]
2. [4, 2, 0]
3. [6, 4, 2] ✓
4. [6, 4, 2, 0]
5. [6, 4, 2, 0, -2]

Question 19

Which of the following is not a valid loop in Python ?

1. for
2. while
3. do-while ✓
4. if-else ✓

Question 20

Which of the following statement(s) will terminate the whole loop and proceed to the statement following the loop ?

1. pass
2. break ✓
3. continue
4. goto

Question 21

Which of the following statement(s) will terminate only the current pass of the loop and proceed with the next iteration of the loop?

1. pass
2. break
3. continue ✓
4. goto

Question 22

Function range(3) is equivalent to :

1. range(1, 3)
2. range(0, 3) ✓
3. range(0, 3, 1) ✓
4. range(1, 3, 0)

Question 23

Function range(3) will yield an iteratable sequence like

1. [0, 1, 2] ✓
2. [0, 1, 2, 3]
3. [1, 2, 3]
4. [0, 2]

Question 24

Function range(0, 5, 2) will yield on iterable sequence like

1. [0, 2, 4] ✓
2. [1, 3, 5]
3. [0, 1, 2, 5]
4. [0, 5, 2]

Question 25

Function range(10, 5, -2) will yield an iterable sequence like

1. [10, 8, 6] ✓
2. [9, 7, 5]
3. [6, 8, 10]
4. [5, 7, 9]

Question 26

Function range(10, 5, 2) will yield an iterable sequence like

1. [] ✓
2. [10, 8, 6]
3. [2, 5, 8]
4. [8, 5, 2]

Question 27

Consider the loop given below :

for i in range(-5) :
    print(i)

How many times will this loop run?

1. 5
2. 0 ✓
3. infinite
4. Error

Question 28

Consider the loop given below :

for i in range(10, 5, -3) :
    print(i)

How many times will this loop run?

1. 3
2. 2 ✓
3. 1
4. Infinite

Question 29

Consider the loop given below :

for i in range(3) :
    pass

What will be the final value of i after this loop ?

1. 0
2. 1
3. 2 ✓
4. 3

Question 30

Consider the loop given below :

for i in range(7, 4, -2) :
    break

What will be the final value of i after this loop ?

1. 4
2. 5
3. 7 ✓
4. -2

Question 31

In for a in __________ : , the blank can be filled with

1. an iterable sequence ✓
2. a range( ) function ✓
3. a single value
4. an expression

Question 32

Which of the following are entry controlled loops ?

1. if
2. if-else
3. for ✓
4. while ✓

Question 33

Consider the loop given below. What will be the final value of i after the loop?

for i in range(10) :
    break

1. 10
2. 0 ✓
3. Error
4. 9

Question 34

The else statement can be a part of .......... statement in Python.

1. if ✓
2. def
3. while ✓
4. for ✓

Question 35

Which of the following are jump statements ?

1. if
2. break ✓
3. while
4. continue ✓

Question 36

Consider the following code segment :

for i in range(2, 4):
    print(i)

What values(s) are printed when it executes?

1. 2
2. 3
3. 2 and 3 ✓
4. 3 and 4
5. 2, 3 and 4

Question 37

When the following code runs, how many times is the line "x = x * 2" executed?

x = 1
while ( x < 20 ):
    x = x * 2

1. 2
2. 5 ✓
3. 19
4. 4
5. 32

Question 38

What is the output when this code executes ?

x = 1
while (x <= 5):
    x + 1
print(x)

1. 6
2. 1
3. 4
4. 5
5. no output ✓

Question 39

How many times does the following code execute ?

x = 1
while (x <= 5):
    x + 1
print (x)

1. 6
2. 1
3. 4
4. 5
5. infinite ✓

Question 40

What is the output produced when this code executes?

i = 1
while (i <= 7):
    i*= 2
print (i)

1. 8 ✓
2. 16
3. 4
4. 14
5. no output

Question 41

Consider the following loop:

j = 10
while j >= 5:
    print("X")
    j=j-1

Which of the following for loops will generate the same output as the loop shown previously?

1. for j in range(-1, -5, -1):
       print("X")
2. for j in range(0, 5):
       print("X")
3. for j in range(10, -1, -2):
       print("X") ✓
4. for j in range(10, 5):
       print("X")
5. for j in range(10, 5, -1):
       print("X")

Question 42

What is the output produced when this code executes?

a = 0
for i in range(4,8):
    if i % 2 == 0:
        a = a + i
print (a) 

1. 4
2. 8
3. 10 ✓
4. 18

Question 43

Which of the following code segments contain an example of a nested loop?

1. for i in range(10):
       print(i)
   for j in range(10):
       print(j)
2. for i in range(10):
       print(i)
       for j in range(10):
           print(j) ✓
3. for i in range(10):
       print(i)
       while i < 20:
           print(i)
           i = i + 1 ✓
4. for i in range(10):
       print(i)
   while i < 20:
       print(i)

Question 1

An if-else tests less number of conditions than two successive ifs.
True

Question 2

A for loop is termed as a determinable loop.
True

Question 3

The while loop is an exit controlled loop.
False

Question 4

The range( ) creates an iterable sequence.
True

Question 5

The for loop can also tests a condition before executing the loop-body.
False

Question 6

Only if statement can have an else clause.
False

Question 7

A loop can also take an else clause.
True

Question 8

The else clause of a loop gets executed only when a break statement terminates it.
False

Question 9

A loop with an else clause executes its else clause only when the loop terminates normally.
True

Question 10

A loop with an else clause cannot have a break statement.
False

Question 11

A continue statement can replace a break statement.
False

Question 12

For a for loop, an equivalent while loop can always be written.
True

Question 13

For a while loop, an equivalent for loop can always be written.
False

Question 14

The range( ) function can only be used in for loops.
False

Question 15

An if-elif-else statement is equivalent to a nested-if statement.
True

Question 1

What is the common structure of Python compound statements?

Answer

The common structure of a Python compound statement is as shown below:

<compound statement header>:
    <indented body with multiple simple\
     and/or compound statements>

It has the following components:

1. A header line which begins with a keyword and ends with a colon.
2. A body containing a sequence of statements at the same level of indentation.

Question 2

What is the importance of the three programming constructs?

Answer

The importance of the three programming constructs is a given below:

1. Sequence — Statements get executed sequentially.
2. Selection — Execution of statements depends on a condition test.
3. Repetition\Iteration — Repetition of a set of statements depends on a condition test.

Question 3

What is empty statement in Python? What is its need?

Answer

In Python, an empty statement is pass statement. Its syntax is:

pass

When pass statement is encountered, Python does nothing and moves to next statement in the flow of control.

It is needed in those instances where the syntax of the language requires the presence of a statement but where the logic of the program does not.

Question 4

Which Python statement can be termed as empty statement?

Answer

In Python, an empty statement is pass statement. Its syntax is:

pass

Question 5

What is an algorithm?

Answer

An algorithm is defined as the sequence of instructions written in simple English that are required to get the desired results. It helps to develop the fundamental logic of a problem that leads to a solution.

Question 6

What is a flowchart? How is it useful?

Answer

A flowchart is a pictorial representation of an algorithm. It uses boxes of different shapes to represent different types of instructions. These boxes are connected with arrow marks to indicate the flow of operations. It helps in:

1. Communication — The pictorial representation of the flowchart provides better communication. It is easier for the programmer to explain the logic of a program.
2. Effective Analysis — It is a very useful technique, as flowchart is a pictorial representation that helps the programmer to analyze the problem in detail.

Question 7

Draw flowchart for displaying first 10 odd numbers.

Answer

Question 8

What is entry-controlled loop?

Answer

An entry-controlled loop checks the condition at the time of entry. Only if the condition is true, the program control enters the body of the loop.

Question 9

What are the four elements of a while loop in Python?

Answer

The four elements of a while loop in Python are:

1. Initialization Expressions — It initializes the loop control variable and it is given outside the while loop before the beginning of the loop.
2. Test Expression — If its truth value is true then the loop-body gets executed otherwise not.
3. The Body of the Loop — It is the set of statements that are executed repeatedly in loop.
4. Update Expressions — It updates the value of loop control variable and it is given inside the while loop.

Question 10

What is the difference between else clause of if-else and else clause of Python loops?

Answer

The else clause of an if-else statement is executed when the condition of the if statement results into false. The else clause of a loop is executed when the loop is terminating normally i.e., when its test condition has become false for a while loop or when the for loop has executed for the last value in sequence.

Question 11

In which cases, the else clause of a loop does not get executed?

Answer

The else clause of a loop does not get executed if the loop is terminated due to the execution of a break statement inside the loop.

Question 12

What are jump statements? Name them.

Answer

Jump statements are used to unconditionally transfer program control to other parts within a program. Python provides the below jump statements:

1. break
2. continue

Question 13

How and when are named conditions useful?

Answer

Sometimes the conditions being used in the code are complex and repetitive. In such cases, to make the program more readable and maintainable, named conditions can be used.

Question 14

What are endless loops ? Why do such loops occur?

Answer

A loop which continues iterating indefinitely and never stops is termed as an endless or infinite loop. Such loops can occur primarily due to two reasons:

1. Logical errors when the programmer misses updating the value of loop control variable.
2. Purposefully created endless loops that have a break statement within their body to terminate the loop.

Question 15

How is break statement different from continue?

Answer

When the break statement gets executed, it terminates its loop completely and control reaches to the statement immediately following the loop. The continue statement terminates only the current iteration of the loop by skipping rest of the statements in the body of the loop.

Question 1

Rewrite the following code fragment that saves on the number of comparisons:

if (a == 0) : 
  print ("Zero")
if (a == 1) : 
  print ("One")
if (a == 2) : 
  print ("Two")
if (a == 3) : 
  print ("Three")

Answer

if (a == 0) : 
  print ("Zero")
elif (a == 1) :
  print ("One")
elif (a == 2) :
  print ("Two")
elif (a == 3) :
  print ("Three")

Question 2

Under what conditions will this code fragment print "water"?

if temp < 32 :    
   print ("ice")  
elif temp < 212:  
   print ("water")
else :            
   print ("steam")

Answer

When value of temp is greater than or equal to 32 and less than 212 then this code fragment will print "water".

Question 3

What is the output produced by the following code?

x = 1                        
if x > 3 :
   if x > 4 :                
         print ("A", end = ' ')
   else :                    
         print ("B", end = ' ')
elif x < 2:                  
   if (x != 0):
         print ("C", end = ' ')
print ("D")                  

Answer

Output

C D

Explanation

As value of x is 1 so statements in the else part of outer if i.e. elif x < 2: will get executed. The condition if (x != 0) is true so C is printed. After that the statement print ("D") prints D.

Question 4

What is the error in following code? Correct the code:

weather = 'raining'       
if weather = 'sunny' :
   print ("wear sunblock")
elif weather = "snow":    
   print ("going skiing") 
else :                    
   print (weather)        

Answer

In this code, assignment operator (=) is used in place of equality operator (==) for comparison. The corrected code is below:

weather = 'raining'       
if weather == 'sunny' :
   print ("wear sunblock")
elif weather == "snow":    
   print ("going skiing") 
else :                    
   print (weather)

Question 5

What is the output of the following lines of code?

if int('zero') == 0 :       
   print ("zero")            
elif str(0) == 'zero' :          
   print (0)                  
elif str(0) == '0' :         
   print (str(0))             
else:                         
   print ("none of the above")

Answer

The above lines of code will cause an error as in the line if int('zero') == 0 :, 'zero' is given to int() function but string 'zero' doesn't have a valid numeric representation.

Question 6

Find the errors in the code given below and correct the code:

if n == 0
   print ("zero") 
elif : n == 1     
   print ("one")  
elif             
   n == 2:        
   print ("two") 
else n == 3:      
   print ("three")

Answer

The corrected code is below:

if n == 0 : #1st Error
   print ("zero") 
elif n == 1 : #2nd Error
   print ("one")  
elif n == 2: #3rd Error  
   print ("two") 
elif n == 3: #4th Error     
   print ("three")

Question 7

What is following code doing? What would it print for input as 3?

n = int(input( "Enter an integer:" ))
if n < 1 :
  print ("invalid value")
else :
  for i in range(1, n + 1):
    print (i * i)

Answer

The code will print the square of each number from 1 till the number given as input by the user if the input value is greater than 0. Output of the code for input as 3 is shown below:

Enter an integer:3
1
4
9

Question 8

How are following two code fragments different from one another? Also, predict the output of the following code fragments :

(a)

n = int(input( "Enter an integer:" ))
if n > 0 :
    for a in range(1, n + n ) :
        print (a / (n/2))
    else :
        print ("Now quiting")

(b)

n = int(input("Enter an integer:"))
if n > 0 :
    for a in range(1, n + n) :
        print (a / (n/2))
else :
    print ("Now quiting")

Answer

In part (a) code, the else clause is part of the loop i.e. it is a loop else clause that will be executed when the loop terminates normally. In part (b) code, the else clause is part of the if statement i.e. it is an if-else clause. It won't be executed if the user gives a greater than 0 input for n.

Output of part a:

Enter an integer:3
0.6666666666666666
1.3333333333333333
2.0
2.6666666666666665
3.3333333333333335
Now quiting

Output of part b:

Enter an integer:3
0.6666666666666666
1.3333333333333333
2.0
2.6666666666666665
3.3333333333333335

Question 9a

Rewrite the following code fragment using for loop:

i = 100
while (i > 0) :
    print (i)
    i -= 3

Answer

for i in range(100, 0, -3) :
    print (i)

Question 9b

Rewrite the following code fragment using for loop:

while num > 0 :
    print (num % 10)
    num = num/10

Answer

l = [1]
for x in l:
    l.append(x + 1)
    if num <= 0:
        break
    print (num % 10)
    num = num/10

Question 9c

Rewrite the following code fragment using for loop:

while num > 0 :
    count += 1
    sum += num
        num –= 2
        if count == 10 :
            print (sum/float(count))
            break

Answer

for i in range(num, 0, -2):
    count += 1
    sum += i
    if count == 10 :
        print (sum/float(count))
        break

Question 10a

Rewrite following code fragment using while loops :

min = 0
max = num
if num < 0 :
    min = num
    max = 0 # compute sum of integers
            # from min to max

    for i in range(min, max + 1):
        sum += i

Answer

min = 0
max = num
if num < 0 :
    min = num
    max = 0 # compute sum of integers
            # from min to max
    i = min
    while i <= max:
        sum += i
        i += 1

Question 10b

Rewrite following code fragment using while loops :

for i in range(1, 16) :
  if i % 3 == 0 :      
     print (i)

Answer

i = 1
while i < 16:
    if i % 3 == 0 :
        print (i)
    i += 1

Question 10c

Rewrite following code fragment using while loops :

for i in range(4) :
    for j in range(5):
        if i + 1 == j or j + 1 == 4 :
           print ("+", end = ' ')
    else :
        print ("o", end = ' ')
print()

Answer

i = 0
while i < 4:
    j = 0
    while j < 5:
        if i + 1 == j or j + 1 == 4 :
            print ("+", end = ' ')
        j += 1
    else :
        print ("o", end = ' ')
    i += 1
print()

Question 11a

Predict the output of the following code fragments:

count = 0         
while count < 10:
    print ("Hello")
    count += 1

Answer

Output

Hello
Hello
Hello
Hello
Hello
Hello
Hello
Hello
Hello
Hello

Explanation

The while loop executes 10 times so "Hello" is printed 10 times

Question 11b

Predict the output of the following code fragments:

x = 10
y = 0
while x > y: 
   print (x, y)
   x = x - 1
   y = y + 1

Answer

Output

10 0
9 1
8 2
7 3
6 4

Explanation

Question 11c

Predict the output of the following code fragments:

keepgoing = True        
x=100                   
while keepgoing :       
    print (x)
    x = x - 10 
    if x < 50 :
       keepgoing = False

Answer

Output

100
90
80
70
60
50

Explanation

Inside while loop, the line x = x - 10 is decreasing x by 10 so after 5 iterations of while loop x will become 40. When x becomes 40, the condition if x < 50 becomes true so keepgoing is set to False due to which the while loop stops iterating.

Question 11d

Predict the output of the following code fragments:

x = 45
while x < 50 :
    print (x)

Answer

This is an endless (infinite) loop that will keep printing 45 continuously.

As the loop control variable x is not updated inside the loop neither there is any break statement inside the loop so it becomes an infinite loop.

Question 11e

Predict the output of the following code fragments:

for x in [1,2,3,4,5]:
    print (x)

Answer

Output

1
2
3
4
5

Explanation

x will be assigned each of the values from the list one by one and that will get printed.

Question 11f

Predict the output of the following code fragments:

for x in range(5):
   print (x)      

Answer

Output

0
1
2
3
4

Explanation

range(5) will generate a sequence like this [0, 1, 2, 3, 4]. x will be assigned each of the values from this sequence one by one and that will get printed.

Question 11g

Predict the output of the following code fragments:

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

Answer

Output

1
2
3
4
5
6
7
8
9

Explanation

range(1,10) will generate a sequence like this [1, 2, 3, 4, 4, 5, 6, 7, 8, 9]. p will be assigned each of the values from this sequence one by one and that will get printed.

Question 11h

Predict the output of the following code fragments:

for q in range(100, 50, -10):
   print (q)

Answer

Output

100
90
80
70
60

Explanation

range(100, 50, -10) will generate a sequence like this [100, 90, 80, 70, 60]. q will be assigned each of the values from this sequence one by one and that will get printed.

Question 11i

Predict the output of the following code fragments:

for z in range(-500, 500, 100):
    print (z)

Answer

Output

-500
-400
-300
-200
-100
0
100
200
300
400

Explanation

range(-500, 500, 100) generates a sequence of numbers from -500 to 400 with each subsequent number incrementing by 100. Each number of this sequence is assigned to z one by one and then z gets printed inside the for loop.

Question 11j

Predict the output of the following code fragments:

for y in range(500, 100, 100):
    print (" * ", y)

Answer

This code generates No Output.

The for loop doesn't execute as range(500, 100, 100) returns an empty sequence — [ ].

Question 11k

Predict the output of the following code fragments:

x = 10                     
y = 5                     
for i in range(x-y * 2):  
    print (" % ", i)

Answer

This code generates No Output.

Explanation

The x-y * 2 in range(x-y * 2) is evaluated as below:

    x - y * 2
⇒ 10 - 5 * 2
⇒ 10 - 10 [∵ * has higher precedence than -]
⇒ 0

Thus range(x-y * 2) is equivalent to range(0) which returns an empty sequence — [ ].

Question 11l

Predict the output of the following code fragments:

for x in [1,2,3]:
    for y in [4, 5, 6]:
        print (x, y)

Answer

Output

1 4
1 5
1 6
2 4
2 5
2 6
3 4
3 5
3 6

Explanation

For each iteration of outer loop, the inner loop will execute three times generating this output.

Question 11m

Predict the output of the following code fragments:

for x in range(3):        
    for y in range(4):    
       print (x, y, x + y)

Answer

Output

0 0 0
0 1 1
0 2 2
0 3 3
1 0 1
1 1 2
1 2 3
1 3 4
2 0 2
2 1 3
2 2 4
2 3 5

Explanation

For each iteration of outer loop, the inner loop executes four times (with value of y ranging from 0 to 3) generating this output.

Question 11n

Predict the output of the following code fragments:

c = 0
for x in range(10): 
    for y in range(5):
        c += 1
print (c)

Answer

Output

50

Explanation

Outer loop executes 10 times. For each iteration of outer loop, inner loop executes 5 times. Thus, the statement c += 1 is executed 10 * 5 = 50 times. c is incremented by 1 in each execution so final value of c becomes 50.

Question 12

What is the output of the following code?

for i in range(4):
  for j in range(5):
      if i + 1 == j or j + i == 4:
         print ("+", end = ' ')
      else:
         print ("o", end = ' ')
print()

Answer

Output

o + o o + o o + + o o o + + o o + o o +

Explanation

Outer loop executes 4 times. For each iteration of outer loop, inner loop executes 5 times. Therefore, the total number of times body of inner loop gets executed is 4 * 5 = 20. Thats why there are 20 characters in the output (leaving spaces). When the condition is true then + is printed else o is printed.

Question 13

In the nested for loop code below, how many times is the condition of the if clause evaluated?

for i in range(4):
  for j in range(5):
      if i + 1 == j or j + i == 4:
         print ("+", end = ")
      else:
         print ("o", end = ")
print()

Answer

Outer loop executes 4 times. For each iteration of outer loop, inner loop executes 5 times. Therefore, the total number of times the condition of the if clause gets evaluated is 4 * 5 = 20.

Question 14

Which of the following Python programs implement the control flow graph shown?

(a)

while True :
   n = int(input("Enter an int:"))
   if n == A1 :
      continue
   elif n == A2 :
      break
   else :
      print ("what")
else:
   print ("ever")

(b)

while True :
   n = int(input("Enter an int:"))
   if n == A1 :
      continue
   elif n == A2 :
      break
   else :
      print ("what")
print ("ever")

(c)

while True :
   n = int(input("Enter an int:"))
   if n == A1 :
      continue
   elif n == A2 :
      break
print ("what")
print ("ever")

Answer

Python program given in Option (b) implements this flowchart:

while True :
   n = int(input("Enter an int:"))
   if n == A1 :
      continue
   elif n == A2 :
      break
   else :
      print ("what")
print ("ever")

Question 15

Find the error. Consider the following program :

a = int(input("Enter a value: ")) 
while a != 0:
   count = count + 1
   a = int(input("Enter a value: "))
print("You entered", count, "values.")

It is supposed to count the number of values entered by the user until the user enters 0 and then display the count (not including the 0). However, when the program is run, it crashes with the following error message after the first input value is read :

  Enter a value: 14
  Traceback (most recent call last):
    File "count.py", line 4, in <module> 
      count = count + 1
  NameError: name 'count' is not defined

What change should be made to this program so that it will run correctly ? Write the modification that is needed into the program above, crossing out any code that should be removed and clearly indicating where any new code should be inserted.

Answer

The line count = count + 1 is incrementing the value of variable count by 1 but the variable count has not been initialized before this statement. This causes an error when trying to execute the program. The corrected program is below:

count = 0 #count should be initialized before incrementing
a = int(input("Enter a value: ")) 
while a != 0:
   count = count + 1
   a = int(input("Enter a value: "))
print("You entered", count, "values.")

Question 1

Write a Python script that asks the user to enter a length in centimetres. If the user enters a negative length, the program should tell the user that the entry is invalid. Otherwise, the program should convert the length to inches and print out the result. There are 2.54 centimetres in an inch.

Solution

len = int(input("Enter length in cm: "))
if len < 0:
    print("Invalid input")
else:
    inch = len / 2.54
    print(len, "centimetres is equal to", inch, "inches")

Output

Enter length in cm: 150
150 centimetres is equal to 59.05511811023622 inches

Question 2

A store charges ₹120 per item if you buy less than 10 items. If you buy between 10 and 99 items, the cost is ₹100 per item. If you buy 100 or more items, the cost is ₹70 per item. Write a program that asks the user how many items they are buying and prints the total cost.

Solution

n = int(input("Enter number of items: "))

cost = 0

if n >= 100 :
    cost = n * 70
elif n >= 10 :
    cost = n * 100
else :
    cost = n * 120

print("Total Cost =", cost)

Output

Enter number of items: 58
Total Cost = 5800

Question 3

Write a program that reads from user — (i) an hour between 1 to 12 and (ii) number of hours ahead. The program should then print the time after those many hours, e.g.,
  Enter hour between 1-12 : 9
  How many hours ahead : 4
  Time at that time would be : 1 O'clock

Solution

hr = int(input("Enter hour between 1-12 : "))
n = int(input("How many hours ahead : "))

s = hr + n

if s > 12:
    s -= 12

print("Time at that time would be : ", s, "O'clock")

Output

Enter hour between 1-12 : 9
How many hours ahead : 4
Time at that time would be :  1 O'clock

Question 4

Write a program that asks the user for two numbers and prints Close if the numbers are within .001 of each other and Not close otherwise.

Solution

a = float(input("Enter first number: "))
b = float(input("Enter second number: "))

d = 0
if a > b :
    d = a - b
else : 
    d = b - a

if d <= 0.001 :
    print("Close")
else :
    print("Not Close")

Output

Enter first number: 10.12345
Enter second number: 10.12354
Close

Question 5

A year is a leap year if it is divisible by 4, except that years divisible by 100 are not leap years unless they are also divisible by 400. Write a program that asks the user for a year and prints out whether it is a leap year or not.

Solution

year = int(input("Enter year: "))

if year % 400 == 0 :
    print(year, "is a Leap Year")
elif year % 100 == 0 :
    print(year, "is not a Leap Year")
elif year % 4 == 0 :
    print(year, "is a Leap Year")
else :
    print(year, "is not a Leap Year")

Output

Enter year: 1800
1800 is not a Leap Year

Question 6

Write a program to input length of three sides of a triangle. Then check if these sides will form a triangle or not.
(Rule is: a+b>c;b+c>a;c+a>b)

Solution

a = int(input("Enter first side : "))
b = int(input("Enter second side : "))
c = int(input("Enter third side : "))

if a + b > c and b + c > a and a + c > b :
    print("Triangle Possible")
else :
    print("Triangle Not Possible")

Output

Enter first side : 3
Enter second side : 5
Enter third side : 6
Triangle Possible

Question 7

Write a short program to input a digit and print it in words.

Solution

d = int(input("Enter a digit(0-9): "))

if d == 0 :
    print("Zero")
elif d == 1 :
    print("One")
elif d == 2 :
    print("Two")
elif d == 3 :
    print("Three")
elif d == 4 :
    print("Four")
elif d == 5 :
    print("Five")
elif d == 6 :
    print("Six")
elif d == 7 :
    print("Seven")
elif d == 8 :
    print("Eight")
elif d == 9 :
    print("Nine")
else :
    print("Invalid Digit")

Output

Enter a digit(0-9): 6
Six

Question 8

Write a short program to check whether square root of a number is prime or not.

Solution

import math

n = int(input("Enter a number: "))
sr = math.sqrt(n)
c = 0

for i in range(1, int(sr + 1)) :
    if (sr % i == 0) :
        c += 1

if c == 2 :
    print("Square root is prime")
else :
    print("Square root is not prime")

Output

Enter a number: 49
Square root is prime

Question 9

Write a short program to print first n odd numbers in descending order.

Solution

n = int(input("Enter n: "))
x = n * 2 - 1

for i in range(x, 0, -2) :
    print(i)

Output

Enter n: 5
9
7
5
3
1

Question 10

Write a short program to print the following series :

(i) 1 4 7 10 .......... 40.
(ii) 1 -4 7 -10 .......... -40

Solution

print("First Series:")
for i in range(1, 41, 3) :
    print(i, end = ' ')

print("\nSecond Series:")
x = 1
for i in range(1, 41, 3) :
    print(i * x, end = ' ')
    x *= -1

Output

First Series:
1 4 7 10 13 16 19 22 25 28 31 34 37 40 
Second Series:
1 -4 7 -10 13 -16 19 -22 25 -28 31 -34 37 -40

Question 11

Write a short program to find average of list of numbers entered through keyboard.

Solution

sum = count = 0

print("Enter numbers")
print("(Enter 'q' to see the average)")

while True :
    n = input()
    if n == 'q' or n == 'Q' :
        break
    else :
        sum += int(n)
        count += 1

avg = sum / count
print("Average = ", avg)

Output

Enter numbers
(Enter 'q' to see the average)
2
5
7
15
12
q
Average =  8.2

Question 12

Write a program to input 3 sides of a triangle and print whether it is an equilateral, scalene or isosceles triangle.

Solution

a = int(input("Enter first side : "))
b = int(input("Enter second side : "))
c = int(input("Enter third side : "))

if a == b and b == c :
    print("Equilateral Triangle")
elif a == b or b == c or c == a:
    print("Isosceles Triangle")
else :
    print("Scalene Triangle")

Output

Enter first side : 10
Enter second side : 5
Enter third side : 10
Isosceles Triangle

Question 13

Write a program to take an integer a as an input and check whether it ends with 4 or 8. If it ends with 4, print "ends with 4", if it ends with 8, print "ends with 8", otherwise print "ends with neither".

Solution

a = int(input("Enter an integer: "))

if a % 10 == 4 :
    print("ends with 4")
elif a % 10 == 8 :
    print("ends with 8")
else :
    print("ends with neither")

Output

Enter an integer: 18
ends with 8

Question 14

Write a program to take N (N > 20) as an input from the user. Print numbers from 11 to N. When the number is a multiple of 3, print "Tipsy", when it is a multiple of 7, print "Topsy". When it is a multiple of both, print "TipsyTopsy".

Solution

n = int(input("Enter a number greater than 20: "))
if n <= 20 :
    print("Invalid Input")
else :
    for i in range(11, n + 1) :
        print(i)
        if i % 3 == 0 and i % 7 == 0 :
            print("TipsyTopsy")
        elif i % 3 == 0 :
            print("Tipsy")
        elif i % 7 == 0 :
            print("Topsy")

Output

Enter a number greater than 20: 25
11
12
Tipsy
13
14
Topsy
15
Tipsy
16
17
18
Tipsy
19
20
21
TipsyTopsy
22
23
24
Tipsy
25

Question 15

Write a short program to find largest number of a list of numbers entered through keyboard.

Solution

print("Enter numbers:")
print("(Enter 'q' to see the result)")

l = input()

if l != 'q' and l != 'Q' :
    l = int(l)
    while True:
        n = input()
        if n == 'q' or n == 'Q' :
            break
        n = int(n)
        if n > l :
            l = n
    print("Largest Number =", l)

Output

Enter numbers:
(Enter 'q' to see the result)
3
5
8
2
4
q
Largest Number = 8

Question 16

Write a program to input N numbers and then print the second largest number.

Solution

n = int(input("How many numbers you want to enter? "))
if n > 1 :
    l = int(input())   # Assume first input is largest
    sl = int(input())  # Assume second input is second largest
    if sl > l :
        t = sl
        sl = l
        l = t
    for i in range(n - 2) :
        a = int(input())
        if a > l :
            sl = l
            l = a
        elif a > sl :
            sl = a
    print("Second Largest Number =", sl)
else :
    print("Please enter more than 1 number")

Output

How many numbers you want to enter? 5
55
25
36
12
18
Second Largest Number = 36

Question 17

Given a list of integers, write a program to find those which are palindromes. For example, the number 4321234 is a palindrome as it reads the same from left to right and from right to left.

Solution

print("Enter numbers:")
print("(Enter 'q' to stop)")

while True :
    n = input()
    if n == 'q' or n == 'Q' :
        break
    n = int(n)
    t = n
    r = 0
    while (t != 0) :
        d = t % 10
        r = r * 10 + d
        t = t // 10
    if (n == r) :
        print(n, "is a Palindrome Number")
    else :
        print(n, "is not a Palindrome Number")

Output

Enter numbers:
(Enter 'q' to stop)
67826
67826 is not a Palindrome Number
4321234
4321234 is a Palindrome Number
256894
256894 is not a Palindrome Number
122221
122221 is a Palindrome Number
q

Question 18

Write a complete Python program to do the following :

(i) read an integer X.

(ii) determine the number of digits n in X.

(iii) form an integer Y that has the number of digits n at ten's place and the most significant digit of X at one's place.

(iv) Output Y.

(For example, if X is equal to 2134, then Y should be 42 as there are 4 digits and the most significant number is 2).

Solution

x = int(input("Enter an integer: "))
temp = x
count = 0
digit = -1

while temp != 0 :
    digit = temp % 10
    count += 1
    temp = temp // 10

y = count * 10 + digit

print("Y =", y)

Output

Enter an integer: 2134
Y = 42

Question 19

Write a Python program to print every integer between 1 and n divisible by m. Also report whether the number that is divisible by m is even or odd.

Solution

m = int(input("Enter m: "))
n = int(input("Enter n: "))
for i in range(1, n) :
    if i % m == 0 :
        print(i, "is divisible by", m)
        if i % 2 == 0 :
            print(i, "is even")
        else :
            print(i, "is odd")

Output

Enter m: 3
Enter n: 20
3 is divisible by 3
3 is odd
6 is divisible by 3
6 is even
9 is divisible by 3
9 is odd
12 is divisible by 3
12 is even
15 is divisible by 3
15 is odd
18 is divisible by 3
18 is even

Question 20a

Write Python programs to sum the given sequences:

2/9 - 5/13 + 8/17 ...... (print 7 terms)

Solution

n = 2 #numerator initial value
d = 9 #denominator initial value
m = 1 #to add/subtract alternate terms
sum = 0

for i in range(7) :
    t = n / d
    sum += t * m
    n += 3
    d += 4
    m *= -1
    
print("Sum =", sum)

Output

Sum = 0.3642392586003134

Question 20b

Write Python programs to sum the given sequences:

1² + 3² + 5² + ..... + n² (Input n)

Solution

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

i = 1
sum = 0

while i <= n :
    sum += i ** 2
    i += 2

print("Sum =", sum)

Output

Enter the value of n: 9
Sum = 165

Question 21

Write a Python program to sum the sequence:

1 + 1/1! + 1/2! + 1/3! + ..... + 1/n! (Input n)

Solution

n = int(input("Enter the value of n: "))
sum = 0

for i in range(n + 1) :
    fact = 1
    for j in range(1, i) :
        fact *= j
    term = 1 / fact
    sum += term

print("Sum =", sum)

Output

Sum = 3.708333333333333

Question 22

Write a program to accept the age of n employees and count the number of persons in the following age group:

(i)    26 - 35
(ii)   36 - 45
(iii)  46 - 55

Solution

n = int(input("Enter the value of n: "))
g1 = g2 = g3 = 0

for i in range(1, n + 1) :
    age = int(input("Enter employee age: "))
    #We have used chained comparison operators
    if 26 <= age <= 35 :
        g1 += 1
    elif 36 <= age <= 45 :
        g2 += 1
    elif 46 <= age <= 55 :
        g3 += 1

print("Employees in age group 26 - 35: ", g1)
print("Employees in age group 36 - 45: ", g2)
print("Employees in age group 46 - 55: ", g3)

Output

Enter the value of n: 10
Enter employee age: 45
Enter employee age: 53
Enter employee age: 28
Enter employee age: 32
Enter employee age: 34
Enter employee age: 49
Enter employee age: 30
Enter employee age: 38
Enter employee age: 33
Enter employee age: 53
Employees in age group 26 - 35:  5
Employees in age group 36 - 45:  2
Employees in age group 46 - 55:  3

Question 23a

Write programs to find the sum of the following series:

x - x²/2! + x³/3! - x⁴/4! + x⁵/5! - x⁶/6! (Input x)

Solution

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

sum = 0
m = 1

for i in range(1, 7) :
    fact = 1
    for j in range(1, i+1) :
        fact *= j
    term = x ** i / fact
    sum += term * m
    m = m * -1

print("Sum =", sum)

Output

Enter the value of x: 2
Sum = 0.8444444444444444

Question 23b

Write programs to find the sum of the following series:

x + x²/2 + x³/3 + ...... + xⁿ/n (Input x and n both)

Solution

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

sum = 0

for i in range(1, n + 1) :
    term = x ** i / i
    sum += term

print("Sum =", sum)

Output

Enter the value of x: 2
Enter the value of n: 5
Sum = 17.066666666666666

Question 24a

Write programs to print the following shapes:

   *
  * *
 * * *
  * *
   *

Solution

n = 3 # number of rows

# upper half
for i in range(n) :
    for j in range(n, i+1, -1) : 
        print(' ', end = '')
    for k in range(i+1) :
        print('*', end = ' ')
    print()

# lower half
for i in range(n-1) :
    for j in range(i + 1) : 
        print(' ', end = '')
    for k in range(n-1, i, -1) :
        print('*', end = ' ')
    print()

Output

  * 
 * * 
* * *
 * *
  *

Question 24b

Write programs to print the following shapes:

*
* *
* * *
* *
*

Solution

n = 3 # number of rows

# upper half
for i in range(n) :
    for k in range(i+1) :
        print('*', end = ' ')
    print()

# lower half
for i in range(n-1) :
    for k in range(n-1, i, -1) :
        print('*', end = ' ')
    print()

Output

* 
* * 
* * *
* *
*

Question 24c

Write programs to print the following shapes:

   *
 *  *
*    *
 *  *
   *

Solution

n = 3 # number of rows

# upper half
for i in range(1, n+1) :
    # for loop for initial spaces
    for j in range(n, i, -1) :
        print(' ', end = '')

    #while loop for * and spaces
    x = 1
    while x < 2 * i :
        if x == 1 or x == 2 * i - 1 :
            print('*', end = '')
        else :
            print(' ', end = '')
        x += 1
    print()

# lower half
for i in range(n-1, 0, -1) :
    # for loop for initial spaces
    for j in range(n, i, -1) :
        print(' ', end = '')

    #while loop for * and spaces
    x = 1
    while x < 2 * i :
        if x == 1 or x == 2 * i - 1 :
            print('*', end = '')
        else :
            print(' ', end = '')
        x += 1
    print()

Output

  *
 * *
*   *
 * *
  *

Question 24d

Write programs to print the following shapes:

*
* *
*   *
*     *
*   *
* *
*

Solution

n = 4 # number of row

#upper half
for i in range(1, n+1) :
    #while loop for * and spaces
    x = 1
    while x < 2 * i :
        if x == 1 or x == 2 * i - 1 :
            print('*', end = '')
        else :
            print(' ', end = '')
        x += 1
    print()

#lower half
for i in range(n-1, 0, -1) :
    #while loop for * and spaces
    x = 1
    while x < 2 * i :
        if x == 1 or x == 2 * i - 1 :
            print('*', end = '')
        else :
            print(' ', end = '')
        x += 1
    print()

Output

*
* *
*   *
*     *
*   *
* *
*

Question 25a

Write programs using nested loops to produce the following patterns:

A
A B
A B C
A B C D
A B C D E
A B C D E F

Solution

n = 6

for i in range(n) :
    t = 65
    for j in range(i + 1) :
        print(chr(t), end = ' ')
        t += 1
    print()

Output

A 
A B 
A B C
A B C D
A B C D E
A B C D E F

Question 25b

Write programs using nested loops to produce the following patterns:

A
B B
C C C
D D D D
E E E E E

Solution

n = 5
t = 65

for i in range(n) :
    for j in range(i + 1) :
        print(chr(t), end = ' ')
    t += 1
    print()

Output

A 
B B 
C C C
D D D D
E E E E E

Question 25c

Write programs using nested loops to produce the following patterns:

0
2 2
4 4 4
6 6 6 6
8 8 8 8 8

Solution

for i in range(0, 10, 2):
    for j in range(0, i + 1, 2) :
        print(i, end = ' ')
    print()

Output

0 
2 2 
4 4 4
6 6 6 6
8 8 8 8 8

Question 25d

Write programs using nested loops to produce the following patterns:

2
4 4
6 6 6
8 8 8 8

Solution

for i in range(2, 10, 2) :
    for j in range(2, i + 1, 2) :
        print(i, end = ' ')
    print()

Output

2 
4 4 
6 6 6
8 8 8 8

Question 26

Write a program using nested loops to produce a rectangle of *'s with 6 rows and 20 *'s per row.

Solution

for i in range(6) :
    for j in range(20) :
        print('*', end = '')
    print()

Output

********************
********************
********************
********************
********************
********************

Question 27

Given three numbers A, B and C, write a program to write their values in an ascending order. For example, if A = 12, B = 10, and C = 15, your program should print out:

Smallest number = 10
Next higher number = 12
Highest number = 15

Solution

a = int(input("Enter first number: "))
b = int(input("Enter second number: "))
c = int(input("Enter third number: "))

if a < b and a < c :
    small = a
    if b < c :
        middle = b
        large = c
    else :
        middle = c
        large = b
elif b < a and b < c :
    small = b
    if a < c :
        middle = a
        large = c
    else :
        middle = c
        large = a
else :
    small = c
    if a < b :
        middle = a
        large = b
    else :
        middle = b
        large = a


print("Smallest number =", small)
print("Next higher number =", middle)
print("Highest number =", large)

Output

Enter first number: 10
Enter second number: 5
Enter third number: 15
Smallest number = 5
Next higher number = 10
Highest number = 15

Question 28

Write a Python script to input temperature. Then ask them what units, Celsius or Fahrenheit, the temperature is in. Your program should convert the temperature to the other unit. The conversions are:

F = 9/5C + 32 and C = 5/9 (F 32).

Solution

temp = float(input("Enter Temperature: "))
unit = input("Enter unit('C' for Celsius or 'F' for Fahrenheit): ")

if unit == 'C' or unit == 'c' :
    newTemp = 9 / 5 * temp + 32
    print("Temperature in Fahrenheit =", newTemp)
elif unit == 'F' or unit == 'f' :
    newTemp = 5 / 9 * (temp - 32)
    print("Temperature in Celsius =", newTemp)
else :
    print("Unknown unit", unit)

Output

Enter Temperature: 38
Enter unit('C' for Celsius or 'F' for Fahrenheit): C
Temperature in Fahrenheit = 100.4

Question 29

Ask the user to enter a temperature in Celsius. The program should print a message based on the temperature:

• If the temperature is less than -273.15, print that the temperature is invalid because it is below absolute zero.
• If it is exactly -273.15, print that the temperature is absolute 0.
• If the temperature is between -273.15 and 0, print that the temperature is below freezing.
• If it is 0, print that the temperature is at the freezing point.
• If it is between 0 and 100, print that the temperature is in the normal range.
• If it is 100, print that the temperature is at the boiling point.
• If it is above 100, print that the temperature is above the boiling point.

Solution

temp = float(input("Enter Temperature in Celsius: "))

if temp < -273.15 :
    print("Temperature is invalid as it is below absolute zero")
elif temp == -273.15 :
    print("Temperature is absolute zero")
elif -273.15 <= temp < 0:
    print("Temperature is below freezing")
elif temp == 0 :
    print("Temperature is at the freezing point")
elif 0 < temp < 100:
    print("Temperature is in the normal range")
elif temp == 100 :
    print("Temperature is at the boiling point")
else :
    print("Temperature is above the boiling point")

Output

Enter Temperature in Celsius: -273.15
Temperature is absolute zero

Question 30

Write a program to display all of the integers from 1 up to and including some integer entered by the user followed by a list of each number's prime factors. Numbers greater than 1 that only have a single prime factor will be marked as prime.

For example, if the user enters 10 then the output of the program should be:

Enter the maximum value to display: 10
1 = 1
2 = 2 (prime)
3 = 3 (prime)
4 = 2x2
5 = 5 (prime)
6 = 2x3
7 = 7 (prime)
8 = 2x2x2
9 = 3x3
10 = 2x5

Solution

import math

n = int(input("Enter an integer: "))

for i in range(1, n + 1) :
    if i == 1:
        print("1 = 1")
    else :
        print(i, "=", end=' ')
        c = 0
        for j in range(1, i + 1) :
            if i % j == 0:
                c += 1
        if c == 2:
            print(i, "(prime)", end = '')
            print()
        else :
            t = i
            while t % 2 == 0 :
                print("2", end='x')
                t = t // 2
            k = 3
            x = math.ceil(math.sqrt(t)) + 1
            while k <= x :
                while (t % k == 0) :
                    print(k, end='x')
                    t = t // k
                k += 2

            if t > 2 :
                print(t, end='x')
                
            print()

Output

Enter an integer: 10
1 = 1
2 = 2 (prime)
3 = 3 (prime)
4 = 2x2x
5 = 5 (prime)
6 = 2x3x
7 = 7 (prime)
8 = 2x2x2x
9 = 3x3x
10 = 2x5x