Chapter 1: Review of Python Class 12 Computer Science NCERT Solutions

Class 12 Computer Science (Python) – Chapter 1 – Review of Python

NCERT Textbook Questions Solved – Class 12 Computer Science (Python)

TOPIC-1: Python Basics

Very Short Answer Type Questions (1 mark)

Question 1. Name the Python Library modules which need to be imported to invoke the following functions: load(), pow()

Answer: pickle, math

Question 2. Name the modules to which the following functions belong: Uniform(), fabs()

Answer: random, math

Question 3. Differentiate between the round() and floor() functions with the help of suitable example. [CBSE Comptt. 2016]

Answer: The function round() is used to convert a fractional number into the nearest whole number, whereas the function floor() is used to convert to the nearest lower whole number. For example: round(5.8) = 6, round(4.1) = 5, floor(6.9) = 6, floor(5.01) = 5.

Short Answer Type Questions (2 marks)

Question 1. Out of the following, find those identifiers, which cannot be used for naming Variables or functions in a Python program:

Total * Tax, While, Class, Switch, 3rd Row, finally, Column 31, Total

Answer: Total * Tax, Class, 3rd Row, finally

Question 2. Name the Python Library modules which need to be imported to invoke the following functions: sqrt(), dump()

Answer: math, pickle

Question 3. Out of the following, find the identifiers, which cannot be used for naming Variable or Functions in a Python program: [CBSE Delhi 2016]

_Cost, Price*Qty, float, switch, Address one, Delete, Number12, do

Answer: Price*Qty, float, Address one, do

Question 4. Out of the following find those identifiers, which cannot be used for naming Variable or Functions in a Python Program:

Days * Rent, For, A_price, Grand Total, do, 2Clients, Participant1, My city

Answer: Illegal variable or function names are Days * Rent, For, do, 2Clients, and Grand Total because they either use keywords, have spaces/operators, or start with an integer.

Question 5. Name the function/method required for [CBSE SQP 2015]:

Finding second occurrence of ‘m’ in “madam”.
Get the position of an item in the list.

Answer: find, index

Question 6. Which string method is used to implement the following:

To count the number of characters in the string: len(str)
To change the first character of the string into capital letter: str.capitalize()
To check whether a given character is a letter or a number: ch.isalnum()
To change lowercase to uppercase letter: str.upper()
Change one character into another character: str.replace(old, new)

Question 7. What is the difference between input() and raw_input()?

Answer: raw_input() takes the input as a string, whereas input() automatically determines the correct type based on user input. Use input() when expecting an integer and raw_input() when expecting a string.

Question 8. What are the two ways of output using print()?

Answer: Ordinarily, each print statement produces one line of output. You can end the print statement with a trailing comma to combine the results of multiple print statements into a single line.

Question 9. Why does the expression 2 + 3*4 result in the value 14 and not the value 24?

Answer: Operator precedence rules make the expression to be interpreted as 2 + (3*4), hence the result is 14.

Question 10. How many times will Python execute the code inside the following while loop? Justify your answers.

Code:
i = 0
while i < 0 and i > 2:
    print(“Hello …”)
    i = i + 1

Answer: 0 times. The condition i < 0 and i > 2 is never true, so the loop body is never executed.

Question 11. How many times will Python execute the code inside the following while loop?

Code:
i = 1
while i < 10000 and i > 0 and 1:
    print(“Hello …”)
    i = 2 * i

Answer: 14

Question 12. Convert the following for loop into a while loop:

Code:
for i in range(1, 100):
    if i % 4 == 2:
        print(i, “mod”, 4, “= 2”)

Answer:
i = 1
while i < 100:
    if i % 4 == 2:
        print(i, “mod”, 4, “= 2”)
    i = i + 1

Question 13. Convert the following for loop into while loop:

Code:
for i in range(10):
    for j in range(i):
        print(‘$’)
    print(“”)

Answer:
i = 0
while i < 10:
    j = 0
    while j < i:
        print(‘$’)
        j = j + 1
    print(“”)
    i = i + 1

Question 14. Rewrite the following for loop into while loop: [CBSE Text Book]

Code:
for a in range(25, 500, 25):
    print(a)

Answer:
a = 25
while a < 500:
    print(a)
    a = a + 25

Question 15. Rewrite the following for loop into while loop: [CBSE Text Book]

Code:
for a in range(90, 9, -9):
    print(a)

Answer:
a = 90
while a > 9:
    print(a)
    a = a – 9

Question 16. Convert the following while loop into for loop:

Code:
i = 0
while i < 100:
    if i % 2 == 0:
        print(i, “is even”)
    else:
        print(i, “is odd”)
    i = i + 1

Answer:
for i in range(100):
    if i % 2 == 0:
        print(i, “is even”)
    else:
        print(i, “is odd”)

Very Short Answer Type Questions (1 mark)

Question 1: Name the Python Library modules which need to be imported to invoke the following functions: load() and pow()

Answer: load() – pickle, pow() – math

Question 2: Name the modules to which the following functions belong: uniform() and fabs()

Answer: uniform() – random, fabs() – math

Question 3: Differentiate between the round() and floor() functions with suitable examples.

Answer: round() rounds a number to the nearest integer, while floor() returns the greatest integer less than or equal to the number.
Example: round(5.8) = 6, round(4.1) = 4; floor(6.9) = 6, floor(5.01) = 5

Short Answer Type Questions (2 marks)

Question 1: Out of the following, find identifiers which cannot be used in a Python program: Total * Tax, While, Class, Switch, 3rd Row, finally, Column 31, Total

Answer: Total * Tax, Class, 3rd Row, finally

Question 2: Name the Python Library modules for the following functions: sqrt() and dump()

Answer: sqrt() – math, dump() – pickle

Question 3: Find the invalid identifiers from the list: _Cost, Price*Qty, float, switch, Address one, Delete, Number12, do

Answer: Price*Qty, float, Address one, do

Question 4: Find identifiers which cannot be used: Days * Rent, For, A_price, Grand Total, do, 2Clients, Participant1, My city

Answer: Days * Rent, For, Grand Total, do, 2Clients

Question 5: Name the functions used for: Finding second occurrence of ‘m’ in “madam”, Get the position of an item in a list

Answer: find(), index()

Question 6: String methods used for:

1. Count characters – len(str)
2. Capitalize first letter – str.capitalize()
3. Check if alphanumeric – str.isalnum()
4. Convert to uppercase – str.upper()
5. Replace character – str.replace(old, new)

Question 7: Difference between input() and raw_input()

Answer: raw_input() returns string input. input() evaluates the input and returns data in correct type (used in Python 2.x). In Python 3.x, input() behaves like raw_input().

Question 8: Two ways of output using print()

Answer: 1. Normal print with newline
2. Print using end=”” to continue on same line

Question 9: Why does 2 + 3*4 evaluate to 14?

Answer: Due to operator precedence: 3*4 is evaluated first, then added to 2 → result is 14

Question 10: Number of executions for:

Code:
i = 0
while i < 0 and i > 2:
    print(“Hello …”)
    i += 1

Answer: 0 times (condition is false initially)

Question 11: Number of executions for:

Code:
i = 1
while i < 10000 and i > 0 and 1:
    print(“Hello …”)
    i = 2 * i

Answer: 14 times

Question 12: Convert for loop into while loop:

Code:
i = 1
while i < 100:
    if i % 4 == 2:
        print(i, “mod”, 4, “= 2”)
    i += 1

Question 13: Convert nested for loop into while loop:

Code:
i = 0
while i < 10:
    j = 0
    while j < i:
        print(‘$’, end=”)
        j += 1
    print()
    i += 1

Question 14: Rewrite for a in range(25, 500, 25):

Answer:
a = 25
while a < 500:
    print(a)
    a += 25

Question 15: Rewrite for a in range(90, 9, -9):

Answer:
a = 90
while a > 9:
    print(a)
    a -= 9

Question 16: Convert the while loop into for loop:

Code:
for i in range(100):
    if i % 2 == 0:
        print(i, “is even”)
    else:
        print(i, “is odd”)

Question 17: Convert the while loop into for loop:

Code:
char = “”
print(“Press Tab Enter to stop …”)
for iteration in range(99):
    if char != ‘t’:
        print(“Continue?”)
        char = input()

Question 18: Rewrite while loop:

Answer:
for i in range(10, 250, 50):
    print(i)

Question 19: Rewrite while loop:

Answer:
for i in range(88, 7, -8):
    print(i)

Question 20: Print series 10 to 300:

Answer:
for i in range(10, 301, 10):
    print(i)

Question 21: Print series 105 to 7:

for i in range(105, 6, -7):
    print(i)

Question 22: While loop for 5 to 100 (step 5):

i = 5
while i <= 100:
    print(i)
    i += 5

Question 23: Loop execution count:

for a in range(100, 10, -10):

Answer: 9 times

Question 24: Loop execution count:

i = 100
while i <= 200:
    print(i)
    i += 20

Answer: 6 times

Question 25: Is the statement true?
if (ch1 == ch2): print(“Equal”)

Answer: True

Question 26: Logical operators in Python

Answer: and, or, not

Question 27: Difference between ‘/’ and ‘//’

Answer:
/ – Normal division
// – Floor division

Question 28: Ways to import module

Answer:
1. import math
2. from math import sqrt

Question 29: Parameters vs Arguments

Answer:
Parameters – in function header
Arguments – in function call

Question 30: What are default arguments?

Answer: Parameters with default values in function definition

Question 31: What are keyword arguments?

Answer: Arguments passed by name instead of position

Question 32: Advantages of keyword arguments

Answer:
1. No need to remember order
2. Only needed parameters can be passed

Question 33: What does ‘in’ do?

Answer: Checks membership in a sequence.
Example: ‘Hell’ in ‘Hello World’ → True

Question 34: What does ‘not in’ do?

Answer: Checks if an item is not present in a sequence

Question 35: What does slice do?

Answer: Extracts part of a string using indices.
Example: s[0:4] → ‘Hell’ if s = “Hello World”

Question 36: What is the use of negative indices in slicing?

Answer: Python counts from the end (right) if negative indices are given.
Example:
S = “Hello”
print(S[:-3]) → He
print(S[-3:]) → llo

Question 37: Explain find() function?

Answer: find(sub[, start[, end]])
This function is used to search the first occurrence of the substring in the given string. It returns the index at which the substring starts. It returns -1 if the substring doesn’t occur.
Example:
str = “computer”
str.find(“om”) → 1

Question 38: What are the differences between arrays and lists?

Answer:
– An array holds a fixed number of values, while a list can be dynamically resized.
– An array holds values of a single data type. A list can hold values of mixed data types.

Question 39: What is the difference between a tuple and a list?

Answer:
– A tuple is immutable; a list is mutable.
– A tuple cannot be changed after creation; a list can be modified.
– Tuple uses parentheses (); list uses square brackets [].
Example:
Tuple: a = (2, 4, 5)
List: a = [2, 4, 5]

Question 40: Explain the output of the following code with respect to the scope of the variables.

Code:
x = 5
def func2():
    x = 3
    global x
    x = x + 1
    print(x)
print(x)

Output:
6
3

Explanation:
– The global x statement inside func2() accesses the global variable x and increments it.
– Hence, x = 5 + 1 → 6.
– When x = 3 is used, it creates a local variable, which does not affect the global x.
– So, 6 and then 3 is printed.

Question 41: Explain the two strategies employed by Python for memory allocation. [CBSE SQP 2016]

Answer: Python uses two strategies:
1. Reference Counting: Tracks the number of references to an object. When it reaches zero, the object is deleted.
2. Automatic Garbage Collection: Python reclaims unused memory when the number of allocations minus deallocations crosses a threshold.

Question 42: Rewrite the following code in Python after removing all syntax errors:

Code:
for Name in [“Amar”, “Shveta”, “Parag”]:
    if Name[0] == ‘S’:
        print(Name)

Question 43: Rewrite the following code in Python after removing all syntax errors:

Code:
for Name in [“Ramesh”, “Suraj”, “Priya”]:
    if Name[0] == ‘S’:
        print(Name)

Question 44: What will be the output of the following python code and explain try-except usage:

Code:
Start = 0
while True:
    try:
        Number = int(raw_input(“Enter Number”))
        break
    except ValueError:
        start += 2
        print(“Re-enter an integer”)
print(start)

Answer:
If user enters:
AMAR → Re-enter an integer
THREE → Re-enter an integer
A123 → Re-enter an integer
12006 → Correct entry

Output: 6

Explanation: The try block checks for valid integer input. If invalid (causes ValueError), control moves to except, increments start by 2, and prompts again.

Question 45: Give the output of the following with justification:

Code:
x = 3
x += x – x
print(x)

Answer: 3
Explanation: x = 3 + 3 – 3 = 3

Question 11. Write the output from the following code:

s = 0
for I in range(10, 2, -2):
    s += I
print(“sum=”, s)

Answer: sum= 28

Question 12. Write the output from the following code:

n = 50
i = 5
s = 0
while i < n:
    s += i
    i += 10
print(“i=”, i)
print(“sum=”, s)

Answer: i= 55, sum= 125

Question 13. Same as Question 12 – Duplicate

Answer: i= 55, sum= 125

Question 14. Predict output for random code execution:

Code:
import random
x = 3
N = random.randint(1, x)
for i in range(N):
    print(i, ‘#’, i + 1)

Answer:
Minimum number of executions: 1
Maximum number of executions: 3
Not expected output: 3#4

Question 15. Write the output of the following function:

Code:
def Findoutput():
    L = “earn”
    x = “”
    count = 1
    for i in L:
        if i in [‘a’, ‘e’, ‘i’, ‘o’, ‘u’]:
            x = x + i.swapcase()
        else:
            if (count % 2 != 0):
                x = x + str(len(L[:count]))
            else:
                x = x + i
        count += 1
    print(x)
Findoutput()

Answer: EA3n

Question 16. Output of the following:

Numbers = [9, 18, 27, 36]
for N in Numbers:
    print(N, “#”, end=” “)
print()

Answer: 9 # 18 # 27 # 36 #

Question 17. Predict outputs of random execution:

import random
PICK = random.randint(0, 3)
CITY = [“DELHI”, “MUMBAI”, “CHENNAI”, “KOLKATA”]
for I in CITY:
    for J in range(1, PICK):
        print(I, end=” “)
    print()

Answer:
Max value of PICK: 3
Min value of PICK: 0
Possible Outputs: Option (i) and (iii) valid

Question 18. Output of nested loop:

Values = [10, 20, 30, 40]
for val in Values:
    for I in range(1, val % 9):
        print(I, “*”, end=” “)
    print()

Answer:
1 * 2 * 3 * 4 * 5 * 6 * 7 * 8 *
1 * 2 *
1 * 2 * 3 *
1 * 2 * 3 * 4 *

Question 19. Leap year check:

y = 2000
if y % 4 == 0:
    print(“Leap Year”)
else:
    print(“Not leap year”)

Answer: Leap Year

Question 20. Output of multiplication table:

for i in range(1, 10):
    for j in range(1, 10):
        print(i * j, end=” “)
    print()

Answer:
1 2 3 4 5 6 7 8 9
2 4 6 8 10 12 14 16 18
3 6 9 12 15 18 21 24 27
…
9 18 27 36 45 54 63 72 81

Question 21. Print with syntax correction:

Incorrect:
print(‘Radhsa’s dress is pretty’)

Correct:
print(“Radhsa’s dress is pretty”)

Question 22. Replace character in string:

str = ‘Honesty is the best policy’
print(str.replace(‘o’, ‘*’))

Answer: H*nesty is the best p*licy

Question 23. Check title case:

str = ‘Hello Python’
print(str.istitle())

Answer: True

Question 24. Left strip characters:

str = ‘Hello Python’
print(str.lstrip(“Hel”))

Answer: lo Python

Question 25. Dictionary methods:

A = {10:1000, 20:2000, 30:3000, 40:4000, 50:5000}
print(A.items())
print(A.keys())
print(A.values())

Answer:
Items: [(10, 1000), (20, 2000), (30, 3000), (40, 4000), (50, 5000)]
Keys: [10, 20, 30, 40, 50]
Values: [1000, 2000, 3000, 4000, 5000]

Question 26. Length of a tuple:

t = (10, 20, 30, 40, 50)
print(len(t))

Answer: 5

Question 27. Max and min in a tuple:

t = (‘a’, ‘b’, ‘c’, ‘A’, ‘B’)
print(max(t))
print(min(t))

Answer:
max: ‘c’
min: ‘A’

Question 28. Max and min in numbers:

T = (10, 30, 2, 50, 5, 6, 100, 65)
print(max(T))
print(min(T))

Answer:
max: 100
min: 2

Question 29. Comparing tuples (Python 2.x):

T1 = (10, 20, 30, 40, 50)
T2 = (10, 20, 30, 40, 50)
T3 = (100, 200, 300)
cmp(T1, T2)
cmp(T2, T3)
cmp(T3, T1)

Answer:
0
-1
1
(Note: cmp() is not available in Python 3)

Question 30. Tuple concatenation:

T1 = (10, 20, 30, 40, 50)
T2 = (100, 200, 300)
T3 = T1 + T2
print(T3)

Answer: (10, 20, 30, 40, 50, 100, 200, 300)

Question 31.

t = tuple()
t = t + (‘Python’,)
print(t)
print(len(t))
t1 = (10, 20, 30)
print(len(t1))

Answer:
(‘Python’,)
1
3

Question 32.

Corrected Code:

for student in [“Jaya”, “Priya”, “Gagan”]:
    if student[0] == ‘S’:
        print(student)

Question 33.

Values = [11, 22, 33, 44]
for V in Values:
    for NV in range(1, V % 10):
        print(NV, V)

Answer:
1 11
1 22
2 22
1 33
2 33
3 33
1 44
2 44
3 44
4 44

Question 34.

import random
SEL = random.randint(0, 3)
ANIMAL = [“DEER”, “Monkey”, “COW”, “Kangaroo”]
for A in ANIMAL:
    for AA in range(1, SEL):
        print(A, end=””)
    print()

Answer:
Possible outputs vary.
If SEL = 3:
DEERDEER
MonkeyMonkey
COWCOW
KangarooKangaroo
Maximum SEL: 3
Minimum SEL: 0
Correct option: (iv)

TOPIC-3: Random Functions

Question 1:

What are the possible outcome(s) executed from the following code? Also specify the maximum and minimum values that can be assigned to the variable PICKER.

import random
PICKER = random.randint(0, 3)
COLOR = [“BLUE”, “PINK”, “GREEN”, “RED”]
for I in COLOR:
    for J in range(1, PICKER):
        print(I, end=” “)
    print()

Options:
(i)
BLUE
PINK
GREEN
RED
(ii)
BLUE PINK GREEN RED
(iii)
PINK PINK
GREEN GREEN
RED RED
(iv)
BLUEBLUE
BLUEPINK
PINKGREEN
REDRED

Answer:
Option (i) and (iv) are possible.
Maximum value of PICKER: 3
Minimum value of PICKER: 0

Question 2:

What are the possible outcome(s) expected from the following Python code? Also specify the maximum and minimum value, which we can have.

import random
def main():
    p = “MY PROGRAM”
    i = 0
    while p[i] != “R”:
        l = random.randint(0, 3) + 5
        print(p[l], “-“, end=” “)
        i += 1

Options:
(i) R – P – O – R –
(ii) P – O – R – Y –
(iii) O – R – A – G –
(iv) A – G – R – M –

Answer:
Minimum value = 5
Maximum value = 8
Only Option (iii) is valid.

TOPIC-4: Correcting the Errors

Question 1:

Rewrite the following Python code after removing all syntax errors.

Incorrect:
def main():
    r = raw-input(‘enter any radius : ’)
    a = pi * math.pow(r,2)
    print “ Area = ” + a

Corrected Code:
import math
pi = 3.14
def main():
    r = input(“Enter any radius: “)
    a = pi * math.pow(float(r), 2)
    print(“Area =”, a)

Question 2:

str = “Hello Python”
str[6] = ‘S’

Answer: Strings are immutable in Python. Use slicing:
str = str[:6] + “S” + str[7:]

Question 3:

T = [a, b, c]
print(T)

Answer: Variables not defined. Use strings:
T = [‘a’, ‘b’, ‘c’]
print(T)

Question 4:

Incorrect:
for i in 1 to 100:
    print(i)

Corrected:
for i in range(1, 101):
    print(i)

Question 5:

Incorrect:
i = 10
while [i <= n]:
    print(i)
    i += 10

Corrected:
i = 10
n = 100
while i <= n:
    print(i)
    i += 10

Question 6:

Incorrect:
if (a > b)
    print a:
else if (a < b)
    print b:
else
    print “both are equal”

Corrected:
if a > b:
    print(a)
elif a < b:
    print(b)
else:
    print(“both are equal”)

Question 7:

Incorrect:
c = dict()
n = input(“Enter total number”)
i = 1
while i <= n:
    a = raw_input(“enter place”)
    b = raw_input(“enter number”)
    c[a] = b
    i = i + 1
print “place”, “t”, “number”
for i in c:
    print i, “t”, c[a[i]]

Corrected:
c = dict()
n = int(input(“Enter total number: “))
i = 1
while i <= n:
    a = input(“Enter place: “)
    b = input(“Enter number: “)
    c[a] = b
    i += 1
print(“PlacetNumber”)
for i in c:
    print(i, “t”, c[i])

Question 8:

class info:
    ips = 0
    def __str__(self):
        return “Welcome to the Info Systems”
    def __init__(self):
        self._Systemdate = “”
        self.SystemTime = “”
    def getinput(self):
        self.Systemdate = input(“Enter date: “)
        self.SystemTime = input(“Enter time: “)
    def incrips(self):
        info.ips += 1

i. Invoke Function 1:
print(I)

ii. Error Explanation:
_Systemdate is private, should be accessed using self._Systemdate or through a method.

TOPIC – 5: Short Programs

Q1: Area of Rectangle

length = float(input(“Enter length: “))
breadth = float(input(“Enter breadth: “))
print(“Area of rectangle =”, length * breadth)

Q2: Roots of a Quadratic Equation

import math
a = float(input(“Enter coefficient of x^2: “))
b = float(input(“Enter coefficient of x: “))
c = float(input(“Enter constant term: “))
d = b**2 – 4*a*c
if d == 0:
    print(“Roots are real and equal”)
    root1 = root2 = -b / (2*a)
elif d > 0:
    print(“Roots are real and distinct”)
    root1 = (-b + math.sqrt(d)) / (2*a)
    root2 = (-b – math.sqrt(d)) / (2*a)
else:
    print(“Roots are imaginary”)
print(“Roots of the equation are:”, root1, “and”, root2)

Q3: Print All Factors of a Number

n = int(input(“Enter the number: “))
for i in range(1, n + 1):
    if n % i == 0:
        print(i, “is a factor of”, n)

Q4: Armstrong Number Check

n = int(input(“Enter a number: “))
savedn = n
sum = 0
while n > 0:
    a = n % 10
    sum += a**3
    n = n // 10
if savedn == sum:
    print(savedn, “is an Armstrong Number”)
else:
    print(savedn, “is not an Armstrong Number”)

Q5: Check Prime Number

n = int(input(“Enter the number: “))
flag = 0
for i in range(2, n):
    if n % i == 0:
        flag = 1
        break
if flag == 0:
    print(n, “is prime”)
else:
    print(n, “is composite”)

Q6: Decimal to Binary

dec = int(input(“Enter the decimal to convert: “))
binary = “”
while dec > 0:
    binary = str(dec % 2) + binary
    dec = dec // 2
print(“Binary of the number is:”, binary)

Q7: Binary to Decimal

binary = input(“Enter binary number: “)
decimal = 0
for i in range(len(binary)):
    power = len(binary) – i – 1
    decimal += int(binary[i]) * (2 ** power)
print(“Decimal value is:”, decimal)

Q8: Sum of Two Complex Numbers

a_real = int(input(“Enter real part of first complex number: “))
a_img = int(input(“Enter imaginary part: “))
b_real = int(input(“Enter real part of second complex number: “))
b_img = int(input(“Enter imaginary part: “))
total_real = a_real + b_real
total_img = a_img + b_img
print(“Sum =”, total_real, “+ i”, total_img)

Q9: Product of Two Complex Numbers

a = int(input(“Enter real part of first complex number: “))
b = int(input(“Enter imaginary part: “))
c = int(input(“Enter real part of second complex number: “))
d = int(input(“Enter imaginary part: “))
real = a*c – b*d
img = a*d + b*c
print(“Product =”, real, “+ i”, img)

Q10: Sum of Digits

n = int(input(“Enter the number: “))
sum = 0
while n > 0:
    digit = n % 10
    sum += digit
    n = n // 10
print(“Sum of digits =”, sum)

Question 11. Write a program to find the reverse of a number.

n = int(input(“Enter the number: “))
rev = 0
while n > 0:
    a = n % 10
    rev = (rev * 10) + a
    n = n // 10
print(“Reversed number =”, rev)

Question 12. Write a program to print the pyramid.

for i in range(1, 6):
    for j in range(1, i + 1):
        print(i, end=” “)
    print()

Question 13. Check username and password.

username = input(“Enter username: “)
password = input(“Enter password: “)
if username.strip() == “XXX”:
    if password == “123”:
        print(“Login successful”)
    else:
        print(“Password Incorrect”)
else:
    print(“Username Incorrect”)

Question 14. Write a generator function generatesq()

import math
def generatesq(n):
    for i in range(100, n):
        yield math.sqrt(i)
for val in generatesq(105):
    print(val)

Question 15. Write a method in Python to find and display the prime numbers between 2 to n.

def prime(N):
    for a in range(2, N):
        for i in range(2, a):
            if a % i == 0:
                break
        else:
            print(a)

Question 16. (Repeated same as Question 13)

Already answered above.

Question 17. String methods for specific tasks

To count characters: len(str)
To capitalize first character: str.capitalize() or str.title()
To check if character is letter/number: str.isalpha() or str.isdigit()
To convert to uppercase: str.upper()
To replace a character: str.replace(old, new)

Question 18. Write a program to input a string and find number of words.

s = input(“Enter a string: “)
words = s.split()
print(“Number of words:”, len(words))

Question 19. Write a program to input n numbers and insert a number at a particular position.

n = int(input(“Enter number of values: “))
num = []
for i in range(n):
    number = int(input(“Enter the number: “))
    num.append(number)
newno = int(input(“Enter the number to be inserted: “))
pos = int(input(“Enter position: “))
num.insert(pos, newno)
print(num)

Question 20. Write a program to input n numbers and search a number.

n = int(input(“Enter number of values: “))
num = []
for i in range(n):
    number = int(input(“Enter the number: “))
    num.append(number)
search = int(input(“Enter number to be searched: “))
flag = False
for i in range(n):
    if num[i] == search:
        print(search, “found at position”, i)
        flag = True
        break
if not flag:
    print(search, “not found in list”)

Question 21. Write a program to search a customer number in phonebook.

def printlist(s):
    for i in range(len(s)):
        print(i, s[i])
phonenumbers = [‘9840012345’, ‘9840011111’, ‘9845622222’, ‘9850012345’, ‘9884412345’]
number = input(“Enter the phone number to be searched: “).strip()
try:
    i = phonenumbers.index(number)
    print(“Phone number found at index”, i)
except ValueError:
    print(“Phone number not found in phonebook”)
print(“PHONEBOOK”)
printlist(phonenumbers)

Question 22. Reverse a list without built-in function.

n = int(input(“Enter number of values: “))
num = []
for i in range(n):
    number = int(input(“Enter the number: “))
    num.append(number)
for i in range(n // 2):
    num[i], num[n-i-1] = num[n-i-1], num[i]
print(“Reversed list:”, num)

Question 23. Output of the Client class program:

class Client:
    def __init__(self, ID=1, NM=”Noname”):
        self.CID = ID
        self.Name = NM
    def Allocate(self, changelD, Title):
        self.CID = self.CID + changelD
        self.Name = Title + self.Name
    def Display(self):
        print(self.CID, “#”, self.Name)

C1 = Client()
C2 = Client(102)
C3 = Client(205, “Fedrick”)
C1.Display()
C2.Display()
C3.Display()
C2.Allocate(4, “Ms.”)
C3.Allocate(2, “Mr.”)
C1.Allocate(1, “Mrs.”)
C1.Display()
C2.Display()
C3.Display()

Output:
1 # Noname
102 # Noname
205 # Fedrick
2 # Mrs.Noname
106 # Ms.Noname
207 # Mr.Fedrick

Question 24. Output and explanation of try-except usage.

count = 0
while True:
    try:
        number = int(input(“Input a Number: “))
        break
    except ValueError:
        count += 2
        print(count, “Re-enter Number”)

Explanation: If the user inputs a non-integer, the except block increases count by 2 and prompts again.

Question 25. Write a method in Python to display prime numbers between 2 to N.

def prime(N):
    for a in range(2, N):
        is_prime = True
        for i in range(2, int(a**0.5) + 1):
            if a % i == 0:
                is_prime = False
                break
        if is_prime:
            print(a)

Question 1. (Stack Program for String Reversal)

class mystack:
    def __init__(self):
        self.mystr = input(“Enter the string: “)
        self.mylist = list(self.mystr)
    def display(self):
        if len(self.mylist) > 0:
            print(“Reversed string using stack:”)
            while self.mylist:
                print(self.mylist.pop(), end=””)
            print()
        else:
            print(“Stack is empty”)

Sample Output:
Enter the string: Python
Reversed string using stack:
nohtyP

Explanation:
A stack works on the principle of LIFO (Last In, First Out). Using pop() in a loop reverses the string efficiently.