This blog post will explore 20 essential Python programs frequently asked in coding interviews. These questions cover a wide range of topics, including basic string manipulation, arrays, numbers, and problem-solving techniques. Whether you're a beginner looking to get your feet wet or an experienced programmer aiming to improve your skills, these Python interview coding questions and answers will help you prepare for your next interview and increase your chances of landing your dream job. Let's get coding!

# 1. Python Program to Swap Two Variables

## Program Steps

1. Initialize two variables with distinct values.

2. Swap the values of these variables.

3. Display the values of the variables before and after swapping.

## Code Program

```
# Step 1: Initialize two variables
a = 5
b = 10
print(f"Before swapping: a = {a}, b = {b}")
# Step 2: Swap the values using tuple unpacking
a, b = b, a
# Step 3: Display the values after swapping
print(f"After swapping: a = {a}, b = {b}")
```

### Output:

Before swapping: a = 5, b = 10 After swapping: a = 10, b = 5

### Explanation:

1. The program starts by defining two variables, *a* and *b*, with initial values of 5 and 10, respectively. These variables represent the data that will be swapped.

2. Python allows for a straightforward swapping mechanism using tuple unpacking. By assigning *a, b = b, a*, Python effectively creates a tuple of the right-hand side expressions (*b, a*) and unpacks it into the left-hand side variables. This operation swaps their values without needing a temporary variable.

3. Finally, the program prints the values of *a* and *b* both before and after the swap. This demonstrates the simplicity and elegance of swapping variables in Python, showcasing an operation that is more verbose and error-prone in many other programming languages.

# 2. Python Program to Check if a Number is Prime

## Program Steps

1. Prompt the user to enter a number.

2. Check if the number is less than 2, in which case it is not prime.

3. For numbers 2 and above, check for factors from 2 to the square root of the number. If any divisor is found, the number is not prime.

4. If no divisors are found, the number is prime.

5. Display the result to the user.

## Code Program

```
# Step 1: Prompt the user for a number
num = int(input("Enter a number: "))
# Function to check if a number is prime
def is_prime(n):
# Step 2: Numbers less than 2 are not prime
if n < 2:
return False
# Step 3: Check for factors from 2 up to the square root of n
for i in range(2, int(n**0.5) + 1):
if n % i == 0:
return False
return True
# Step 4: Determine if the number is prime and display the result
if is_prime(num):
print(f"{num} is a prime number.")
else:
print(f"{num} is not a prime number.")
```

### Output:

Enter a number: 11 11 is a prime number.

### Explanation:

1. The user is prompted to input a number, which is read as an integer and stored in the variable *num*.

2. The program defines a function *is_prime* that checks if the given number *n* is prime. It first verifies if *n* is less than 2, in which case it immediately returns *False* because numbers less than 2 are not prime by definition.

3. For numbers 2 and above, the function checks for divisors by iterating from 2 up to the square root of *n* (inclusive). This range is sufficient because if *n* has a factor larger than its square root, then it must also have a factor smaller than the square root, and the function would have found it by this point.

4. If the function finds a divisor in this range, it returns *False*, indicating that *n* is not prime. If no divisors are found, the function returns *True*, indicating that *n* is prime.

5. Based on the return value of *is_prime*, the program prints out whether the entered number is prime or not, providing a straightforward way to determine the primality of a number in Python.

# 3. Python Program to Find the Factorial of a Number

## Program Steps

1. Prompt the user to enter a non-negative integer.

2. Check if the entered number is less than 0; if so, print an error message.

3. If the number is 0 or 1, its factorial is 1.

4. For numbers greater than 1, calculate the factorial by multiplying all integers from 2 to the number itself.

5. Display the factorial of the number.

## Code Program

```
# Step 1: Prompt the user for the number
num = int(input("Enter a number: "))
# Function to calculate factorial
def factorial(n):
# Step 2: Base case for factorial(0) and factorial(1)
if n == 0 or n == 1:
return 1
# Step 3: Recursive case for n > 1
else:
return n * factorial(n - 1)
# Step 4: Check if the user input is negative
if num < 0:
print("Sorry, factorial does not exist for negative numbers.")
else:
# Calculate the factorial of the number
print(f"The factorial of {num} is {factorial(num)}")
```

### Output:

Enter a number: 5 The factorial of 5 is 120

### Explanation:

1. The program begins by asking the user to input a non-negative integer, which will be used to calculate its factorial.

2. A function named *factorial* is defined to calculate the factorial of the number. It uses a simple recursive approach where the factorial of *n* is *n* multiplied by the factorial of *n - 1*. The recursion stops when it reaches base cases where the factorial of 0 or 1 is defined as 1.

3. Before calling the *factorial* function, the program checks if the user has entered a negative number. Since factorials of negative numbers are not defined, it prints an error message in such cases.

4. If the number is non-negative, the program calculates its factorial by calling the *factorial* function and displays the result.

5. This approach demonstrates the use of recursion to solve a problem efficiently, providing a clear example of how to calculate factorials in Python.

# 4. Python Program To Add Two Numbers

Let's write a Python program to add two numbers, demonstrating the simplicity and elegance of performing arithmetic operations in Python.

## Program Steps

1. Prompt the user to input the first number.

2. Prompt the user to input the second number.

3. Convert the input from strings to numbers that can be added together.

4. Add the two numbers.

5. Display the sum to the user.

## Code Program

```
# Step 1: Prompt the user for the first number
first_number = input("Enter the first number: ")
# Step 2: Prompt the user for the second number
second_number = input("Enter the second number: ")
# Step 3: Convert the input strings to integers
first_number = int(first_number)
second_number = int(second_number)
# Step 4: Add the two numbers
sum = first_number + second_number
# Step 5: Display the sum
print("The sum of the two numbers is:", sum)
```

### Output:

Enter the first number: 5 Enter the second number: 7 The sum of the two numbers is: 12

### Explanation:

1. The program starts by asking the user to input two numbers. These inputs are captured as strings by the *input* function.

2. To perform arithmetic operations, these strings must be converted into integers. The program converts the input strings to integers using the *int* function.

3. After conversion, the two numbers are added together using the *+* operator, and the result is stored in the variable *sum*.

4. Finally, the program prints the result, displaying the sum of the two input numbers. This simple program illustrates the basic structure of a Python program and how to perform arithmetic operations and handle user input.

# 5. Maximum of Two Numbers in Python

In Python, determining the maximum of two numbers is a basic operation that can be implemented in various ways. This section will guide you through creating a simple Python program to find the maximum of two user-provided numbers. Understanding how to compare numbers and execute conditional logic is foundational in programming, and this example will help solidify these concepts.

## Program Steps

1. Prompt the user to input two numbers.

2. Convert the input values to the appropriate numerical type (e.g., integers or floating-point numbers) for comparison.

3. Compare the two numbers using a conditional statement to determine which one is greater.

4. Display the maximum number to the user.

## Code Program

```
# Step 1: Prompt the user for two numbers
num1 = float(input("Enter the first number: "))
num2 = float(input("Enter the second number: "))
# Step 2: Compare the numbers and find the maximum
if num1 > num2:
max_num = num1
else:
max_num = num2
# Step 3: Display the maximum number
print("The maximum number is:", max_num)
```

### Output:

Enter the first number: 45 Enter the second number: 32 The maximum number is: 45

### Explanation:

1. The program starts by asking the user to enter two numbers. These are read as strings from the standard input using the *input* function and then converted to floating-point numbers (to accommodate decimal values) using the *float* function.

2. It then compares the two numbers using an *if-else* statement. If *num1* is greater than *num2*, *num1* is assigned to *max_num*. Otherwise, *num2* is assigned to *max_num*.

3. Finally, the program prints out the maximum number using the *print* function. The output shows which of the two input numbers is greater.

# 6. Python Program for Factorial of a Number

The factorial of a number is a fundamental concept in mathematics and computer science, particularly in combinatorics and discrete mathematics. The factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example, the factorial of 5 (5!) is 5 * 4 * 3 * 2 * 1 = 120. The value of 0! is 1, according to the convention for an empty product. This section will guide you through writing a Python program to calculate the factorial of a given number using a simple iterative approach.

## Program Steps

1. Prompt the user to enter a non-negative integer.

2. Check if the entered number is less than 0; if so, print an error message.

3. If the number is 0 or 1, its factorial is 1.

4. For numbers greater than 1, calculate the factorial by multiplying all integers from 2 to the number itself.

5. Display the factorial of the number.

## Code Program

```
# Step 1: Prompt the user to enter a number
num = int(input("Enter a number: "))
# Step 2: Check if the number is negative
if num < 0:
print("Sorry, factorial does not exist for negative numbers")
else:
# Step 3: Initialize the factorial value to 1
factorial = 1
# Step 4: Calculate the factorial for numbers greater than 1
for i in range(1, num + 1):
factorial = factorial * i
# Step 5: Display the result
print(f"The factorial of {num} is {factorial}")
```

### Output:

Enter a number: 5 The factorial of 5 is 120

### Explanation:

1. The program starts by asking the user to input a number. This number is stored as an integer.

2. It then checks if the number is negative. Factorials of negative numbers are not defined, so it prints an error message in such cases.

3. The factorial of 0 and 1 is 1 by definition. Therefore, if the number is 0 or 1, the program sets the factorial to 1.

4. For numbers greater than 1, the program calculates the factorial by iterating through all integers from 1 to the number itself, multiplying each integer by the running total to calculate the factorial.

5. Finally, the program prints the factorial of the number, demonstrating how to calculate factorials using a straightforward iterative approach.

# 7. Python Program for Simple Interest

Simple interest is a quick and easy method of calculating the interest charge on a loan. Simple interest is determined by multiplying the daily interest rate by the principal by the number of days that elapse between payments. This concept is fundamental in finance and is often one of the first lessons in financial literacy. This section will guide you through creating a Python program to calculate simple interest based on principal, rate, and time.

## Program Steps

1. Prompt the user to input the principal amount, the rate of interest per annum, and the time period in years.

2. Calculate the simple interest using the formula *Simple Interest = (Principal * Rate * Time) / 100*.

3. Display the calculated simple interest to the user.

## Code Program

```
# Step 1: Get user input for principal, rate, and time
principal = float(input("Enter the principal amount: "))
rate = float(input("Enter the rate of interest per annum (%): "))
time = float(input("Enter the time period in years: "))
# Step 2: Calculate simple interest
simple_interest = (principal * rate * time) / 100
# Step 3: Display the simple interest
print("The simple interest is:", simple_interest)
```

### Output:

Enter the principal amount: 1000 Enter the rate of interest per annum (%): 5 Enter the time period in years: 2 The simple interest is: 100.0

### Explanation:

1. The program begins by asking the user for the principal amount, the interest rate per annum (as a percentage), and the time period for the loan or investment in years. These inputs are captured using the *input* function and converted to floating-point numbers with the *float* function to ensure that they can be used in mathematical calculations.

2. It calculates the simple interest using the formula *Simple Interest = (Principal * Rate * Time) / 100*. This formula multiplies the principal amount by the annual interest rate and the time period in years, then divides the product by 100 to convert the interest rate from a percentage to a decimal.

3. Finally, the calculated simple interest is printed out to the console, informing the user of the interest amount that will be charged or earned over the specified period.

# 8. Python Program to check Armstrong Number

An Armstrong number (also known as a narcissistic number) is a number that is the sum of its own digits each raised to the power of the number of digits. For example, 153 is an Armstrong number because 1^3 + 5^3 + 3^3 = 153. These numbers are special in mathematics and programming, and checking for them is a common problem in coding exercises. This section will guide you through creating a Python program to check if a given number is an Armstrong number.

## Program Steps

1. Prompt the user to enter a number.

2. Calculate the number of digits in the given number.

3. Sum the powers of each digit according to the number of digits.

4. Check if the sum is equal to the original number.

5. Display whether the entered number is an Armstrong number or not.

## Code Program

```
# Step 1: Prompt the user to input a number
num = int(input("Enter a number: "))
# Step 2: Calculate the number of digits
num_of_digits = len(str(num))
# Step 3: Sum the powers of each digit
sum_of_powers = sum([int(digit) ** num_of_digits for digit in str(num)])
# Step 4: Check if the sum is equal to the original number
if sum_of_powers == num:
print(f"{num} is an Armstrong number.")
else:
print(f"{num} is not an Armstrong number.")
```

### Output:

Enter a number: 153 153 is an Armstrong number.

### Explanation:

1. The user is prompted to enter a number, which is stored as an integer.

2. The program calculates the number of digits in the entered number by converting the number to a string and then using the *len* function.

3. It then calculates the sum of each digit raised to the power of the number of digits in the number. This is achieved by iterating over each digit in the string representation of the number, converting each digit back to an integer, raising it to the power of the number of digits, and summing these values.

4. The program checks if this sum is equal to the original number. If it is, the number is an Armstrong number; otherwise, it is not.

5. Finally, the program prints the result, indicating whether the entered number is an Armstrong number or not.

# 9. Python Program To Print All Prime Numbers in an Interval

Prime numbers are natural numbers greater than 1 that have no positive divisors other than 1 and themselves. Finding prime numbers within a specific interval is a common problem that helps in understanding the fundamentals of number theory and programming logic. This section will guide you through creating a Python program to print all prime numbers within a given interval.

## Program Steps

1. Prompt the user to enter the start and end of the interval.

2. For each number in the interval, check if it is a prime number.

3. To check for a prime number, see if it has any divisor other than 1 and itself.

4. If a number is prime, print it.

## Code Program

```
# Step 1: Get the interval start and end from the user
start = int(input("Enter the start of the interval: "))
end = int(input("Enter the end of the interval: "))
# Function to check if a number is prime
def is_prime(n):
if n <= 1:
return False
for i in range(2, int(n**0.5) + 1):
if n % i == 0:
return False
return True
# Step 2 & 3: Iterate through the interval and print prime numbers
print(f"Prime numbers between {start} and {end} are:")
for num in range(start, end + 1):
if is_prime(num):
print(num, end=' ')
```

### Output:

Enter the start of the interval: 10 Enter the end of the interval: 50 Prime numbers between 10 and 50 are: 11 13 17 19 23 29 31 37 41 43 47

### Explanation:

1. The program begins by asking the user for the start and end points of the interval within which to find prime numbers. These are read from the standard input and converted into integers.

2. A helper function *is_prime* is defined to check if a given number *n* is prime. It first checks if *n* is less than or equal to 1, in which case it returns *False* as the number is not prime. Then, for each number from 2 up to the square root of *n* (inclusive), it checks if *n* is divisible by any of these numbers. If *n* is divisible by any number other than 1 and itself, it is not prime, and the function returns *False*. If no divisors are found, the function returns *True*, indicating that *n* is prime.

3. The program then iterates through each number in the specified interval. For each number, it calls the *is_prime* function. If the function returns *True*, indicating the number is prime, the program prints the number.

4. The output lists all prime numbers within the specified interval, demonstrating the program's ability to identify prime numbers efficiently.

# 10. Python Program To Check Whether a Number Is Prime or Not

A prime number is a natural number greater than 1 that is not a product of two smaller natural numbers. In other words, it has exactly two distinct natural number divisors: 1 and itself. Checking whether a given number is prime or not is a fundamental problem in number theory and has applications in various areas of mathematics and computer science. This section will guide you through creating a Python program to check if a given number is prime.

## Program Steps

1. Prompt the user to enter a number.

2. Check if the number is less than 2, in which case it's not prime.

3. For numbers 2 and greater, check if the number is divisible by any number from 2 to the square root of the given number.

4. If the number is found to be divisible, it's not prime.

5. If the number is not divisible by any number in the range, it's prime.

## Code Program

```
# Step 1: Get the number from the user
num = int(input("Enter a number: "))
# Function to check if the number is prime
def is_prime(n):
# Step 2: Numbers less than 2 are not prime
if n < 2:
return False
# Step 3 & 4: Check for factors from 2 to the square root of n
for i in range(2, int(n**0.5) + 1):
if n % i == 0:
return False
return True
# Check if the entered number is prime and display the result
if is_prime(num):
print(f"{num} is a prime number.")
else:
print(f"{num} is not a prime number.")
```

### Output:

Enter a number: 29 29 is a prime number.

### Explanation:

1. The user is prompted to enter a number, which is read as an integer.

2. The *is_prime* function checks if the number is prime. It first verifies if the number is less than 2, in which case it immediately returns *False* as numbers less than 2 are not prime by definition.

3. For numbers 2 and above, the function checks for divisibility by any number from 2 up to the square root of the given number (*n*). This range is sufficient because if *n* has a factor larger than its square root, then it must also have a factor smaller than the square root, and we would have found it by this point in the loop.

4. If the function finds a divisor in this range, it returns *False*, indicating that *n* is not prime. If no divisors are found, the function returns *True*, indicating that *n* is prime.

5. The main part of the program uses the *is_prime* function to check the entered number and then prints out whether the number is prime or not based on the function's return value.

# 11. Python Program To Find the Area of a Circle

The area of a circle is a fundamental concept in geometry that describes the size of the circle. The formula to calculate the area of a circle is A = πr^2, where A is the area, π (pi) is a constant approximately equal to 3.14159, and r is the radius of the circle. This formula is derived from the properties of a circle and provides a way to calculate the area given the radius. This section will demonstrate how to write a Python program to calculate the area of a circle based on the radius provided by the user.

## Program Steps

1. Prompt the user to enter the radius of the circle.

2. Use the formula A = πr^2 to calculate the area. Use the math module to access the constant π (pi).

3. Display the calculated area to the user.

## Code Program

```
# Step 1: Import the math module to access pi
import math
# Prompt the user to enter the radius of the circle
radius = float(input("Enter the radius of the circle: "))
# Step 2: Calculate the area using the formula A = πr^2
area = math.pi * radius * radius
# Step 3: Display the area
print(f"The area of the circle with radius {radius} is: {area}")
```

### Output:

Enter the radius of the circle: 4 The area of the circle with radius 4.0 is: 50.26548245743669

### Explanation:

1. The program begins by importing the math module, which contains the constant π (pi), necessary for calculating the area of the circle.

2. It then prompts the user to enter the radius of the circle, which is read as a floating-point number to accommodate decimal values.

3. Using the area formula A = πr^2, the program calculates the area. It multiplies π (accessed via math.pi) by the square of the radius.

4. Finally, the program prints the calculated area, providing the user with the area of the circle based on the provided radius. This demonstrates a practical application of mathematical formulas in programming to solve geometric problems.

# 12. Python Program for N-Th Fibonacci Number

The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding ones, usually starting with 0 and 1. Fibonacci numbers are a fascinating subject in mathematics and computer science because of their frequency in nature, their applicability in various algorithms, and their occurrence in complex problem-solving scenarios. This section will guide you through writing a Python program to find the n-th Fibonacci number, utilizing a simple and efficient approach.

## Program Steps

1. Prompt the user to enter the value of n for which the n-th Fibonacci number is required.

2. Initialize the first two Fibonacci numbers (0 and 1) and use a loop to generate the subsequent numbers up to n.

3. In each iteration of the loop, update the values of the two most recent Fibonacci numbers and calculate the next number in the sequence.

4. Continue this process until the n-th Fibonacci number is found.

5. Display the n-th Fibonacci number to the user.

## Code Program

```
# Step 1: Prompt the user for the value of n
n = int(input("Enter the value of n: "))
# Step 2: Initialize the first two Fibonacci numbers
a, b = 0, 1
# Use a loop to find the n-th Fibonacci number
for i in range(2, n):
# Step 3: Calculate the next Fibonacci number
a, b = b, a + b
# Step 4: Check if n is less than or equal to 1 to handle the first two numbers
if n <= 0:
print("Please enter a positive integer.")
elif n == 1:
print("The 1st Fibonacci number is 0.")
else:
# Step 5: Display the n-th Fibonacci number
print(f"The {n}-th Fibonacci number is: {b}")
```

### Output:

Enter the value of n: 10 The 10-th Fibonacci number is: 34

### Explanation:

1. The program starts by asking the user to input the term *n* in the Fibonacci sequence they wish to find.

2. It initializes the first two numbers of the Fibonacci sequence, 0 and 1, using two variables *a* and *b*.

3. Using a loop, it updates these variables to progress through the Fibonacci sequence. In each iteration, *a* takes the value of *b*, and *b* takes the value of *a + b*, effectively moving forward two steps in the sequence.

4. The program also includes a check for the cases where *n* is 0 or 1, as these cases are the base conditions of the Fibonacci sequence and need to be handled separately.

5. After completing the loop or identifying the base condition, the program prints the n-th Fibonacci number. This approach is efficient for calculating Fibonacci numbers without requiring recursion, making it suitable for large values of *n*.

# 13. Python Program to Make a Simple Calculator

## Program Steps

1. Display options for the user to choose the desired arithmetic operation.

2. Prompt the user to enter two numbers on which the operation will be performed.

3. Based on the user's choice, perform the selected operation using the input numbers.

4. Display the result of the operation.

5. Provide an option to perform another calculation or exit the program.

## Code Program

```
# Function to add two numbers
def add(x, y):
return x + y
# Function to subtract two numbers
def subtract(x, y):
return x - y
# Function to multiply two numbers
def multiply(x, y):
return x * y
# Function to divide two numbers
def divide(x, y):
return x / y
while True:
# Step 1: Display operation options
print("Options:")
print("Enter 'add' to add two numbers")
print("Enter 'subtract' to subtract two numbers")
print("Enter 'multiply' to multiply two numbers")
print("Enter 'divide' to divide two numbers")
print("Enter 'exit' to end the program")
# Take input from the user
choice = input("Enter choice: ")
# Step 5: Check if the user wants to exit
if choice == 'exit':
break
# Step 2: Prompt the user for numbers
num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))
# Step 3: Perform the selected operation
if choice == 'add':
print("The result is", add(num1, num2))
elif choice == 'subtract':
print("The result is", subtract(num1, num2))
elif choice == 'multiply':
print("The result is", multiply(num1, num2))
elif choice == 'divide':
if num2 != 0:
print("The result is", divide(num1, num2))
else:
print("Error! Division by zero.")
else:
print("Invalid Input")
```

### Output:

Options: Enter 'add' to add two numbers Enter 'subtract' to subtract two numbers Enter 'multiply' to multiply two numbers Enter 'divide' to divide two numbers Enter 'exit' to end the program Enter choice: add Enter first number: 5 Enter second number: 3 The result is 8

### Explanation:

**1. The program defines four functions, each implementing an arithmetic operation**: addition, subtraction, multiplication, and division. These functions take two arguments and return the result of the operation.

2. It then enters a loop that continuously displays the operation options to the user, takes the user's choice of operation, and prompts the user for two numbers.

3. Based on the user's choice, the corresponding function is called with the input numbers as arguments, and the result is displayed.

4. If the user enters 'divide', the program checks for division by zero to avoid errors.

5. The loop continues until the user chooses to exit by typing 'exit'. This interactive loop allows the user to perform multiple calculations without restarting the program.

6. This simple calculator showcases basic Python syntax and programming concepts, making it a great starter project for beginners.

# 14. Python Program to Check Leap Year

## Program Steps

1. Prompt the user to enter a year.

2. Check if the year is divisible by 4.

3. If the year is a century (divisible by 100), then it must also be divisible by 400 to be a leap year.

4. Based on these conditions, determine if the year is a leap year or not.

5. Display the result to the user.

## Code Program

```
# Step 1: Prompt the user to enter a year
year = int(input("Enter a year: "))
# Step 2 & 3: Determine if it's a leap year
if (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0):
is_leap_year = True
else:
is_leap_year = False
# Step 5: Display the result
if is_leap_year:
print(f"{year} is a leap year.")
else:
print(f"{year} is not a leap year.")
Output:
Enter a year: 2000
2000 is a leap year.
```

### Explanation:

1. The program starts by asking the user to input a year. This input is converted into an integer, as year values are numerical.

**2. To determine if the year is a leap year, the program checks two conditions**: First, the year must be divisible by 4 but not by 100; Second, if the year is a century (divisible by 100), it must also be divisible by 400. These conditions are based on the rules that govern leap years.

3. These checks are performed using a combination of conditional statements (*if*, *and*, *or*) to evaluate the divisibility of the year by 4, 100, and 400.

4. The result of these checks is stored in the boolean variable *is_leap_year*.

5. Finally, the program prints whether the entered year is a leap year or not, providing a clear, user-friendly output. This example demonstrates how to implement conditional logic in Python to solve a practical problem.

# 15. Python Program to Check if a Number is Positive or Negative

## Program Steps

1. Prompt the user to enter a number.

2. Check if the number is positive, negative, or zero using conditional statements.

3. Display the result based on the condition.

## Code Program

```
# Step 1: Prompt the user to enter a number
num = float(input("Enter a number: "))
# Step 2: Use conditional statements to determine if the number is positive, negative, or zero
if num > 0:
print("The number is positive.")
elif num == 0:
print("The number is zero.")
else:
print("The number is negative.")
# No explicit Step 3 in code, as displaying the result is integrated within Step 2
```

### Output:

Enter a number: -5 The number is negative.

### Explanation:

1. The program begins by asking the user to input a number. This number is stored as a floating-point value to accommodate decimal numbers, enhancing the program's flexibility.

2. It then evaluates the input number using a series of *if-elif-else* statements. The first *if* checks if the number is greater than zero, in which case it's positive. The *elif* checks if the number is exactly zero. If neither of these conditions is true, the *else* block executes, indicating that the number is negative.

3. The outcome of the evaluation is printed directly within the conditional statements, informing the user if the entered number is positive, negative, or zero. This example demonstrates the use of conditional statements to make simple decisions based on numerical input, a fundamental skill in programming.

# 16. Python Program to Print the Multiplication Table

The multiplication table is a foundational mathematical concept, essential for learning arithmetic and developing number sense. It lists the products of pairs of natural numbers in a systematic and organized manner, serving as a fundamental tool for both students and educators in mathematics. Programming a solution to generate a multiplication table can help understand loops and conditional statements in Python. This section will demonstrate a Python program designed to print the multiplication table for a number entered by the user, highlighting the practical application of loops in generating structured data output.

## Program Steps

1. Prompt the user to enter the required number for the multiplication table.

2. Use a loop to iterate through the numbers 1 to 10.

3. For each iteration, calculate the product of the base number and the iterator.

4. Display each line of the multiplication table.

## Code Program

```
# Step 1: Prompt the user to enter the number
num = int(input("Enter the number for the multiplication table: "))
# Step 2 & 3: Iterate from 1 to 10 to calculate and print each line of the table
for i in range(1, 11):
# Multiply the base number by the iterator and display the result
print(f"{num} x {i} = {num*i}")
# The loop in Step 2 & 3 inherently covers Step 4 by displaying each multiplication fact
```

### Output:

Enter the number for the multiplication table: 5 5 x 1 = 5 5 x 2 = 10 5 x 3 = 15 5 x 4 = 20 5 x 5 = 25 5 x 6 = 30 5 x 7 = 35 5 x 8 = 40 5 x 9 = 45 5 x 10 = 50

### Explanation:

1. The program initiates by asking the user to input a number, which will be the base for the multiplication table.

2. It then enters a loop, iterating through the numbers 1 to 10. Each iteration represents a line in the multiplication table.

3. Within the loop, the program calculates the product of the base number and the iterator (ranging from 1 to 10) and prints the result in a formatted string that mimics a line in the multiplication table.

4. By iterating from 1 to 10 and printing the product at each step, the program efficiently generates the entire multiplication table for the entered number. This example demonstrates the use of loops to automate repetitive calculations and generate structured outputs, a common task in programming.

# 17. Python Program to Merge Two Dictionaries

## Program Steps

1. Define two dictionaries that you want to merge.

2. Merge the dictionaries using a method that combines them into a single dictionary.

3. Display the merged dictionary.

## Code Program

```
# Step 1: Define two dictionaries
dict1 = {'a': 1, 'b': 2}
dict2 = {'b': 3, 'c': 4}
# Step 2: Merge the dictionaries
# In Python 3.5+, use the {**dict1, **dict2} syntax to merge dictionaries
merged_dict = {**dict1, **dict2}
# Step 3: Display the merged dictionary
print("Merged dictionary:")
print(merged_dict)
```

### Output:

Merged dictionary: {'a': 1, 'b': 3, 'c': 4}

### Explanation:

1. The program begins by initializing two dictionaries, *dict1* and *dict2*, each containing some key-value pairs. The keys in these dictionaries represent identifiers, and the values represent the data associated with these identifiers.

2. To merge the dictionaries, the program uses the *{**dict1, **dict2}* syntax, which is available in Python 3.5 and later. This syntax unpacks the key-value pairs from both dictionaries into a new dictionary. If the same key exists in both dictionaries, the value from the second dictionary (*dict2*) will overwrite the value from the first dictionary (*dict1*).

3. Finally, the program prints the merged dictionary, showing the combination of key-value pairs from both original dictionaries. In the output, it's noticeable that the value of the key *'b'* from *dict2* has overwritten the value of the key *'b'* from *dict1*, demonstrating how conflicts between duplicate keys are resolved in the merging process.

# 18. Python Program to Sort Words in Alphabetic Order

## Program Steps

1. Prompt the user to enter a string of text.

2. Split the text into a list of words.

3. Sort the list of words in alphabetic order.

4. Display the sorted list of words.

## Code Program

```
# Step 1: Prompt the user to enter a string of text
text = input("Enter a text: ")
# Step 2: Split the text into words
words = text.split()
# Step 3: Sort the list of words
words.sort()
# Step 4: Display the sorted words
print("The sorted words are:")
for word in words:
print(word)
```

### Output:

Enter a text: the quick brown fox jumps over the lazy dog The sorted words are: brown dog fox jumps lazy over quick the the

### Explanation:

1. The program starts by asking the user to input a string of text. This text can be a sentence, a paragraph, or any textual content that the user wishes to sort alphabetically.

2. The entered text is then split into a list of words using the *split()* method. This method splits the string at every space, creating a list where each element is a word from the original string.

3. The list of words is sorted in alphabetic order using the *sort()* method. This method rearranges the elements of the list so that they follow a specific order (in this case, alphabetical order).

4. Finally, the program iterates through the sorted list of words and prints each word on a new line. This step effectively displays the words of the original text sorted in alphabetic order.

5. This approach demonstrates how Python's built-in methods can be used to manipulate and organize text data efficiently, making it a valuable tool for text processing tasks.

# 19. Python Program to Solve Quadratic Equations

Solving quadratic equations is a fundamental concept in algebra, where each equation has the form ax^2 + bx + c = 0. The solutions to these equations are given by the quadratic formula: x = [-b ± sqrt(b^2 - 4ac)] / 2a. These solutions can be real or complex numbers. Writing a program to solve quadratic equations not only helps in understanding these mathematical concepts but also demonstrates how programming can be used to automate solving mathematical problems. This blog post will introduce a Python program that solves quadratic equations, emphasizing handling different types of solutions.

## Program Steps

1. Prompt the user to enter the coefficients a, b, and c of the quadratic equation.

2. Calculate the discriminant (D = b^2 - 4ac) to determine the nature of the roots.

3. Based on the discriminant, calculate and display the roots of the equation. The roots can be real and distinct, real and equal, or complex.

4. Handle each case separately and display the solutions accordingly.

## Code Program

```
# Import the sqrt function from the math module for square root calculation
from math import sqrt
# Step 1: Prompt the user to enter the coefficients
a = float(input("Enter coefficient a: "))
b = float(input("Enter coefficient b: "))
c = float(input("Enter coefficient c: "))
# Step 2: Calculate the discriminant
D = b**2 - 4*a*c
# Step 3: Determine the nature of the roots based on the discriminant
if D > 0:
# Two distinct real roots
root1 = (-b + sqrt(D)) / (2*a)
root2 = (-b - sqrt(D)) / (2*a)
print(f"Two distinct real roots: {root1} and {root2}")
elif D == 0:
# One real root
root = -b / (2*a)
print(f"One real root: {root}")
else:
# Complex roots
real_part = -b / (2*a)
imaginary_part = sqrt(-D) / (2*a)
print(f"Two complex roots: {real_part} + {imaginary_part}i and {real_part} - {imaginary_part}i")
```

### Output:

Enter coefficient a: 1 Enter coefficient b: -3 Enter coefficient c: 2 Two distinct real roots: 2.0 and 1.0

### Explanation:

1. The program starts by asking the user to input the coefficients a, b, and c of the quadratic equation ax^2 + bx + c = 0. These inputs are converted to floats to accommodate decimal coefficients.

2. It calculates the discriminant (D) using the formula b^2 - 4ac. The discriminant helps in determining the nature of the roots (real and distinct, real and equal, or complex).

3. Depending on the value of the discriminant, the program proceeds to calculate the roots. If D is positive, there are two distinct real roots, found using the quadratic formula with both the plus and minus versions of the square root of D. If D is zero, there is exactly one real root. If D is negative, the equation has complex roots, which are calculated using the real part (-b/2a) and the imaginary part (sqrt(-D)/2a).

4. Finally, the program prints the roots in a format that clearly indicates whether they are real or complex. This example demonstrates the practical application of conditional statements and mathematical operations to solve real-world problems using Python.

# 20. Python Program to Reverse a Number

Reversing a number involves rearranging its digits in the opposite order. This operation is a common task in programming interviews and competitions, serving as a good exercise for understanding basic arithmetic operations and loops in programming. Reversing a number can also be useful in various mathematical computations and algorithmic solutions. This section will explain how to write a Python program to reverse a number, showcasing an approach that is straightforward and easily understandable.

## Program Steps

1. Prompt the user to enter a number.

2. Initialize a variable to store the reversed number.

3. Use a loop to extract each digit of the number, add it to the reversed number, and remove it from the original number.

4. Display the reversed number.

## Code Program

```
# Step 1: Prompt the user to enter a number
num = int(input("Enter a number: "))
# Step 2: Initialize a variable to store the reversed number
reversed_num = 0
# Step 3: Use a while loop to reverse the number
while num > 0:
digit = num % 10 # Extract the last digit of the number
reversed_num = reversed_num * 10 + digit # Append the digit to the reversed number
num = num // 10 # Remove the last digit from the number
# Step 4: Display the reversed number
print(f"Reversed number: {reversed_num}")
```

### Output:

Enter a number: 12345 Reversed number: 54321

### Explanation:

1. The user is prompted to input a number, which is then stored as an integer. This number will be reversed by the program.

2. A variable, *reversed_num*, is initialized to 0. This variable will accumulate the digits of the input number in reverse order.

3. The program enters a while loop that continues as long as the input number is greater than 0. Inside the loop, the last digit of the number is extracted using the modulus operation (*num % 10*). This digit is then added to *reversed_num*, which is first multiplied by 10 to shift its digits left, making room for the new digit. The input number is then divided by 10 using integer division (*num // 10*), effectively removing its last digit.

4. After the loop completes, the reversed number is fully constructed and is printed out. This approach demonstrates a simple method to reverse a number using arithmetic operations and a loop, providing a clear example of manipulating numerical data in Python.

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