Important CS Programs

# Accept input from user
name = input("Enter your name: ")
# Display output
print("Welcome to Python Programming,", name)

# Explicit type conversion from string to int
num1 = int(input("Enter first number: "))
num2 = int(input("Enter second number: "))

result = num1 + num2
print("The sum is:", result)

p = float(input("Enter Principal amount: "))
r = float(input("Enter Rate of interest: "))
t = float(input("Enter Time in years: "))

# Formula for Simple Interest
si = (p * r * t) / 100
print("Simple Interest:", si)

l = float(input("Enter Length: "))
b = float(input("Enter Breadth: "))

area = l * b
print("Area of Rectangle:", area)

a = 10
b = 20
print(f"Before: a={a}, b={b}")

temp = a
a = b
b = temp

print(f"After: a={a}, b={b}")

a = 5
b = 10
# Tuple unpacking method
a, b = b, a
print("Swapped values:", a, b)

c = float(input("Enter temp in Celsius: "))
# Operator precedence: multiplication/division happens before addition
f = (c * 9/5) + 32
print("Temperature in Fahrenheit:", f)

# This code will fail to run
# print("Hello World"  <-- Missing closing parenthesis
print("To fix: Ensure all parentheses are closed.")

try:
    num = 10
    den = 0
    print(num / den)
except ZeroDivisionError:
    print("Runtime Error: Cannot divide by zero.")

days = int(input("Enter number of days: "))
seconds = days * 24 * 60 * 60
print(f"{days} days = {seconds} seconds")

num = int(input("Enter a number: "))
if num % 2 == 0:
    print("Even Number")
else:
    print("Odd Number")

x = int(input("First: "))
y = int(input("Second: "))
z = int(input("Third: "))

if x >= y and x >= z:
    print("Largest is:", x)
elif y >= x and y >= z:
    print("Largest is:", y)
else:
    print("Largest is:", z)

age = int(input("Enter your age: "))
if age >= 18:
    print("Eligible to vote.")
else:
    print("Not eligible to vote.")

year = int(input("Enter year: "))
# Leap year logic: Divisible by 400 OR (Divisible by 4 AND NOT by 100)
if (year % 400 == 0) or (year % 4 == 0 and year % 100 != 0):
    print("Leap Year")
else:
    print("Not a Leap Year")

ch = input("Enter a character: ")
if ch.isupper():
    print("Uppercase Letter")
elif ch.islower():
    print("Lowercase Letter")
elif ch.isdigit():
    print("Digit")
else:
    print("Special Character")

marks = float(input("Enter marks: "))
if marks >= 90:
    print("Grade A")
elif marks >= 75:
    print("Grade B")
elif marks >= 50:
    print("Grade C")
else:
    print("Grade F")

op = input("Enter operator (+, -, *, /): ")
a = float(input("Num 1: "))
b = float(input("Num 2: "))

if op == '+':
    print(a + b)
elif op == '-':
    print(a - b)
elif op == '*':
    print(a * b)
elif op == '/':
    if b != 0:
        print(a / b)
    else:
        print("Cannot divide by zero")
else:
    print("Invalid operator")

n = int(input("Enter number: "))
if n < 0:
    print("Absolute value:", -n)
else:
    print("Absolute value:", n)

n = int(input("Enter number: "))
if n % 5 == 0 and n % 11 == 0:
    print("Divisible by both")
else:
    print("Not divisible by both")

a = int(input("Angle 1: "))
b = int(input("Angle 2: "))
c = int(input("Angle 3: "))

# Sum of angles must be 180
if a + b + c == 180:
    print("Valid Triangle")
else:
    print("Invalid Triangle")

for i in range(1, 11):
    print(i, end=" ")

n = int(input("Enter N: "))
sum_val = 0
i = 1
while i <= n:
    sum_val += i
    i += 1
print("Sum:", sum_val)

num = int(input("Enter number: "))
fact = 1
for i in range(1, num + 1):
    fact *= i
print("Factorial:", fact)

n = int(input("Enter number: "))
for i in range(1, 11):
    print(f"{n} x {i} = {n*i}")

n = int(input("How many terms? "))
a, b = 0, 1
print("Fibonacci sequence:")
for i in range(n):
    print(a, end=" ")
    a, b = b, a + b

num = int(input("Enter number: "))
is_prime = True

if num > 1:
    for i in range(2, int(num/2)+1):
        if num % i == 0:
            is_prime = False
            break
else:
    is_prime = False

if is_prime:
    print("Prime Number")
else:
    print("Not Prime")

num = int(input("Enter number: "))
rev = 0
while num > 0:
    digit = num % 10
    rev = rev * 10 + digit
    num //= 10
print("Reversed:", rev)

num = int(input("Enter number: "))
total = 0
while num > 0:
    total += num % 10
    num //= 10
print("Sum of digits:", total)

num = int(input("Enter number: "))
temp = num
sum_cubes = 0
while temp > 0:
    digit = temp % 10
    sum_cubes += digit ** 3
    temp //= 10

if num == sum_cubes:
    print("Armstrong Number")
else:
    print("Not Armstrong")

num = int(input("Enter number: "))
original = num
rev = 0
while num > 0:
    rev = rev * 10 + (num % 10)
    num //= 10
    
if original == rev:
    print("Palindrome Number")
else:
    print("Not Palindrome")

rows = 5
for i in range(1, rows+1):
    for j in range(i):
        print("*", end="")
    print() # Newline

rows = 5
for i in range(rows, 0, -1):
    for j in range(i):
        print("*", end="")
    print()

rows = 4
for i in range(1, rows + 1):
    # Print leading spaces
    print(" " * (rows - i), end="")
    # Print numbers
    for j in range(1, i + 1):
        print(j, end=" ")
    print()

n = int(input("Enter N: "))
s = 0.0
for i in range(1, n+1):
    s += 1/i
print("Sum of series:", s)

x = int(input("Enter x: "))
n = int(input("Enter n: "))
s = 0
for i in range(1, n+1):
    s += x**i
print("Result:", s)

for i in range(1, 11):
    if i == 5:
        continue # Skip this iteration
    print(i, end=" ")

target = 5
for i in range(1, 11):
    if i == target:
        print("Found", target)
        break # Exit loop completely

a = int(input("Num 1: "))
b = int(input("Num 2: "))
while b:
    a, b = b, a % b
print("GCD is:", a)

x = int(input("Num 1: "))
y = int(input("Num 2: "))
if x > y:
    greater = x
else:
    greater = y

while True:
    if (greater % x == 0) and (greater % y == 0):
        lcm = greater
        break
    greater += 1
print("LCM is:", lcm)

count = 0
while True:
    ch = input("Enter char (or 'quit' to exit): ")
    if ch == 'quit':
        break
    if ch in 'aeiouAEIOU':
        count += 1
print("Total vowels entered:", count)

s = "Python"
for char in s:
    print(char)

text = input("Enter string: ")
rev_text = text[::-1]
print("Reversed:", rev_text)

s = input("Enter string: ")
# Compare with reverse
if s == s[::-1]:
    print("Palindrome")
else:
    print("Not Palindrome")

s = input("Enter string: ").lower()
v = 0
c = 0
for char in s:
    if char.isalpha():
        if char in "aeiou":
            v += 1
        else:
            c += 1
print(f"Vowels: {v}, Consonants: {c}")

text = "Hello World"
print(text.upper())
print(text.lower())

s = "python programming is fun"
print("Capitalize:", s.capitalize()) # First char only
print("Title:", s.title()) # First char of every word

s = "Computer Science"
print("Found 'Sci' at:", s.find("Sci"))
print("Index of 'o':", s.index("o"))

s = "Python3"
print("Is Alpha?", s.isalpha())
print("Is Digit?", s.isdigit())
print("Is Alnum?", s.isalnum())

s = "banana"
print("Number of 'a':", s.count("a"))

text = "I like Java"
new_text = text.replace("Java", "Python")
print(new_text)

s = "Learn Python Today"
words = s.split() # Splits by space
print("List:", words)

joined = "-".join(words)
print("Joined:", joined)

s = "  hello  "
print(f"Original: '{s}'")
print(f"Stripped: '{s.strip()}'")
print(f"LStrip: '{s.lstrip()}'")

filename = "report.pdf"
if filename.endswith(".pdf"):
    print("It is a PDF file.")
if filename.startswith("report"):
    print("It is a report.")

s = "user@gmail.com"
parts = s.partition("@")
print(parts) # ('user', '@', 'gmail.com')

s = "ABCDEFGHI"
print(s[::2]) # Step of 2

fruits = ["Apple", "Banana", "Cherry"]
print(fruits)
print("First:", fruits[0])
print("Last:", fruits[-1])

nums = [10, 20, 30, 40]
sum_val = 0
for n in nums:
    sum_val += n
print("Sum:", sum_val)

l = [1, 2]
l.append(3)
l.extend([4, 5])
print(l)

l = [10, 30]
l.insert(1, 20) # Insert 20 at index 1
print(l)

l.remove(30) # Remove value 30
print(l)

l = [10, 20, 30]
val = l.pop(1) # Remove index 1
print("Popped:", val)
l.clear()
print("List after clear:", l)

nums = [5, 12, 1, 88, 4]
print("Max:", max(nums))
print("Min:", min(nums))

data = [10, 50, 30, 70, 80, 20]
x = int(input("Search for: "))
found = False
for i in range(len(data)):
    if data[i] == x:
        print("Found at index", i)
        found = True
        break
if not found:
    print("Not found")

l = [1, 2, 1, 3, 1, 4]
print("1 appears:", l.count(1), "times")

nums = [5, 2, 9, 1]
nums.sort()
print("Ascending:", nums)
nums.sort(reverse=True)
print("Descending:", nums)

data = [10, 20, 30, 40, 50]
avg = sum(data) / len(data)
print("Mean:", avg)

sq = [x**2 for x in range(1, 6)]
print(sq)

matrix = [[1, 2], [3, 4]]
print("Element at 1,0:", matrix[1][0])

nums = [1, 2, 3, 4, 5, 6]
evens = []
for n in nums:
    if n % 2 == 0:
        evens.append(n)
print("Evens:", evens)

l = [1, 2, 3]
l.reverse()
print("Reversed:", l)

l = [10, 20, 4, 45, 99]
l.sort()
print("Second largest:", l[-2])

t = (1, 2, 3)
t_single = (1,) # Comma needed for single element
print(t, type(t))
print(t_single, type(t_single))

t = (1, 2, 3)
try:
    t[0] = 10
except TypeError:
    print("Error: Tuples are immutable")

t1 = (1, 2)
t2 = (3, 4)
print("Add:", t1 + t2)
print("Repeat:", t1 * 3)

point = (10, 20)
x, y = point
print(f"X: {x}, Y: {y}")

t = (10, 50, 20)
print("Length:", len(t))
print("Max:", max(t))
print("Min:", min(t))

t = (0, 1, 2, 3, 4, 5)
print(t[2:5])

t = ('a', 'b', 'c')
if 'b' in t:
    print("Found b")

l = [1, 2, 3]
t = tuple(l)
print("Converted to tuple:", t)

t = (10, 20, 30, 20)
print("Index of 20:", t.index(20)) # Finds first occurrence

t = (1, 2, 1, 1, 3)
print("Count of 1:", t.count(1))

d = {"name": "Alice", "age": 16}
print("Name:", d["name"])

d = {"a": 1}
d["b"] = 2 # Add new
d["a"] = 100 # Modify existing
print(d)

d = {"Apple": 100, "Mango": 80}
for k in d:
    print(k, "->", d[k])

d = {"x": 10, "y": 20}
print(d.keys())
print(d.values())
print(d.items())

s = "hello"
d = {}
for char in s:
    if char in d:
        d[char] += 1
    else:
        d[char] = 1
print(d)

d = {"a": 1}
print(d.get("b", "Not Found"))

emps = {"John": 50000, "Doe": 60000}
name = input("Enter name: ")
print("Salary:", emps.get(name, "Unknown Employee"))

d = {"a": 1, "b": 2, "c": 3}
del d["a"]
val = d.pop("b")
print("Deleted value:", val)
print("Dict now:", d)

keys = ['a', 'b', 'c']
d = dict.fromkeys(keys, 0)
print(d)

d1 = {"a": 1}
d2 = {"b": 2}
d1.update(d2)
print("Updated d1:", d1)

import math
r = 5
area = math.pi * r * r
print("Area:", area)

import math
print("Square root of 16:", math.sqrt(16))
print("2 to power 3:", math.pow(2, 3))

import math
n = 4.7
print("Ceil:", math.ceil(n))   # 5
print("Floor:", math.floor(n)) # 4

import math
# math.sin takes radians
print("Sin 90 deg:", math.sin(math.radians(90)))

import random
# Random integer between 1 and 6 inclusive
print("Dice roll:", random.randint(1, 6))

import random
# Random even number between 10 and 20
print(random.randrange(10, 21, 2))

import random
print("Random float:", random.random())

import statistics
data = [10, 20, 30, 40, 50]
print("Mean:", statistics.mean(data))

import statistics
data = [1, 5, 2, 9, 3]
# Median sorts list and picks middle
print("Median:", statistics.median(data))

import statistics
data = [1, 2, 2, 3, 4, 2]
print("Mode:", statistics.mode(data))