Python Exercises

Repetition

PAGE $1$

$1.$ Mark the following statements as true or false:

a$.$ In a counter$-$controlled while loop, it is not necessary to initialize the loop control variable.

b$.$ It is possible that the body of a while loop might not execute at all.

c$.$ In an infinite while loop, the loop condition is initially false, but after the first iteration, it is always

true.

d$.$ The while loop:

j $=0$

while $($j $<=10)$:

j $=$ j $+1$

terminates when j $>10$

e$.$ A sentinel$-$controlled while loop is an event$-$controlled while loop whose termination depends on a

special value.

f$.$ A loop is a control structure that causes certain statements to execute over and over.

g$.$ To read data from a file of an unspecified length, an EOF$-$controlled loop is a good choice.

h$.$ When a while loop terminates, the control first goes back to the statement just before the while

statement, and then the control goes to the statement immediately following the while loop.

$2.$ What is the output of the following Python code?

i $=2$

temp $=1$

while i $<10$:

temp $=$ temp $*($i $1)$

i $=$ i $+1$

$3.$ What is the output of the following Python code?

num $=5$

while $($num $>5)$:

num $=$ num $+2$

print$($num$)$

$4.$ What is the output of the following Python code?

num $=0$

while num $*$ num $<=6*$ num:

num $=$ num $+1$

print$($num $)$

$5.$ When does the following while loop terminate?

num $=4$

while $1<=$ num and num $<=20$:

num $=($num$)+1$

num $=$ float$($num$)$

print$($num$)$

$6.$ Suppose that the input is $1203515286-1.$ What is the output of the following code?

sum $=$ int$($input$($Enter sum: $))$

count $=$ int$($input$($Enter count: $))$

while count $<=4$:

num $=$ int$($input$($Enter num: $))$

sum $=$ sum $+$ num

count $+=1$

print$($Sum $=+$ str$($sum$))$

Python Exercises

Repetition

PAGE $2$

$7.$ Suppose that the input is $34672-1.$ What is the output of the following code?

sum $=$ int$($input$($Enter sum: $))$

num $=$ sum

while num $!=-1$:

num $=$ int$($input$($Enter num: $)$

sum $=$ sum $+2*$ num

print$($Sum $=+$ str$($sum$))$

$8.$ Suppose that the input is $34672-1.$ What is the output of the following code?

num $=$ int$($input$($Enter num: $))$

sum $=$ num

while num $!=-1$:

sum $=$ sum $+2*$ num

num $=$ int$($input$($Enter num: $))$

print$($Sum $=+$ str$($ sum$))$

$9.$ Suppose that the input is: $38357114-1.$What is the output of the following code? Assume all variables

are properly declared.

sum $=0$

number $=$ int$($input$("$Enter numbers to sum $($enter $-1$ to quit$)$: $"))$

while number $!=-1$:

sum $=$ sum $+$ number

num$=$ int$($input$(\text{'}$Enter next number: $\text{'}))$

print$("$sum $=",$sum$)$

$10.$ Correct the following code so that it reads and finds the sum of $20$ numbers:

count $=0$

sum $=0$

while count $<=20$:

num$=$ int$($input$(\text{'}$Enter next number: $\text{'}))$

count $+=1$

sum $+=$ count

$11.$ What is the output of the following program?

x $=4$

y $=5$

z $=$ y $+6$

while $((($z $-$ x$)\%4)!=0)$:

print$($z $,"")$

z $=$ z $+7$

$12.$ Suppose that the input is :$582314759815012176145-999.$ What is the output of the

following program?

count $=0$

num $=$ int$($input$($Enter num: $))$

while num $!=-999$:

count $+=1$

print$($num $\%$ count $+)$

num $=$ int$($input$($Enter num: $))$

print$($

$)$

return $0$

Python Exercises

Repetition

PAGE $3$

$13.$ The following program is designed to input two numbers and output their sum. It asks the user if he$/$she

would like to run the program. If the answer is Y or y$,$ it prompts the user to enter two numbers. After adding

the numbers and displaying the results, it again asks the user if he$/$she would like to add more numbers.

However, the program fails to do so$.$ Correct the program so that it works properly.

print$("$This program adds two numbers."$)$

response $=$ input$("$Would you like to run the program: $($Y$/$y$)")$

while $($response $==\text{'}$Y$\text{'}$ or response $==\text{'}$y$\text{'})$:

num$1=$ int$($input$("$Enter the first number: $"))$

num$2=$ int$($input$("$Enter the second number: $"))$

print$("\%\mathrm{.}2$f $"\%$ num$1,"\%\mathrm{.}2$f $"\%$ num$2,"\%\mathrm{.}2$f $"\%($num$1-$ num$2))$

response $=$ input$("$Would you like to add again: $($Y$/$y$)")$

break

$14.$ What is the output of the following program segment?

count $=1$

while count $+=1<=5$:

print$($count: $+$ str$($count$))$

$15.$ What is the output of the following program segment?

count $=5$

while $($count $>0)$:

count $=$ count$-1$

print$($count$,"")$

$16.$ What is the output of the following program segment?

count $=5$

while count $-=1>0$:

print$($count: $+$ str$($count$))$

$17.$ What is the output of the following program segment?

count $=1$

while $($count $<=5)$:

count $=$ count $+1$

print$(($count $*($count $-2)),"")$

$18.$ What type of loop, such as counter$-$control or sentinel$-$control, will you use in each of the following

situations?

a$.$ Sum the following series: $1+(2/1)+(3/2)+(4/3)+(5/4)+...+(10/9)$

b$.$ Sum the following numbers, except the last number: $17,32,62,48,58,-1$

c$.$ A file contains an employee$$s salary. Update the employee$$s salary.

$19.$ Consider the following for loop:

s $=0$

for j in range$(0,10)$:

s $=$ s $+$ j $*($j $-1)$

In this for loop, identify the loop control variable, the initialization statement, lo