We can concatenate two lists in Python using the +operator or the extend() method.

1. Using the + operator:

This creates a new list by joining two lists together.

a = [1, 2, 3]

b = [4, 5, 6]

res = a + b

print(res)

Output

[1, 2, 3, 4, 5, 6]

2. Using the extend() method:

This adds all the elements of the second list to the first list in-place.

a = [1, 2, 3]

b = [4, 5, 6]

a.extend(b)

print(a)

Output

[1, 2, 3, 4, 5, 6]

The __init__() method is known as a constructor in object-oriented programming (OOP) terminology. It is used to initialize an object’s state when it is created. This method is automatically called when a new instance of a class is instantiated.

Purpose:

• Assign values to object properties.
• Perform any initialization operations.

Example: 

We have created a book_shop class and added the constructor and book() function. The constructor will store the book title name and the book() function will print the book name.

To test our code we have initialized the b object with “Sandman” and executed the book() function. 

class book_shop:

    # constructor
    def __init__(self, title):
        self.title = title

    # Sample method
    def book(self):
        print('The tile of the book is', self.title)


b = book_shop('Sandman')
b.book()
# The tile of the book is Sandman

Lists and tuples are fundamental Python data structures with distinct characteristics and use cases.

List:

• Mutable: Elements can be changed after creation.
• Memory Usage: Consumes more memory.
• Performance: Slower iteration compared to tuples but better for insertion and deletion operations.
• Methods: Offers various built-in methods for manipulation.

Example:

a_list = ["Data", "Camp", "Tutorial"]
a_list.append("Session")
print(a_list)  # Output: ['Data', 'Camp', 'Tutorial', 'Session']Powered By 

Tuple:

• Immutable: Elements cannot be changed after creation.
• Memory Usage: Consumes less memory.
• Performance: Faster iteration compared to lists but lacks the flexibility of lists.
• Methods: Limited built-in methods.

Example:

a_tuple = ("Data", "Camp", "Tutorial")
print(a_tuple)  # Output: ('Data', 'Camp', 'Tutorial') 

Python is a versatile, high-level programming language known for its easy-to-read syntax and broad applications. Here are some of Python’s key features:

• Simple and Readable Syntax: Python’s syntax is clear and straightforward, making it accessible for beginners and efficient for experienced developers.
• Interpreted Language: Python executes code line by line, which helps in debugging and testing.
• Dynamic Typing: Python does not require explicit data type declarations, allowing more flexibility.
• Extensive Libraries and Frameworks: Libraries like NumPy, Pandas, and Django expand Python’s functionality for specialized tasks in data science, web development, and more.
• Cross-Platform Compatibility: Python can run on different operating systems, including Windows, macOS, and Linux.

• A variable created inside a function belongs to the local scope of that function, and can only be used inside that function.
• A variable created in the main body of the Python code is a global variable and belongs to the global scope. Global variables are available from within any scope, global and local.

Python Program to Find the Factorial of a Number

To understand this example, you should have the knowledge of the following Python programming topics:

• Python if…else Statement
• Python for Loop
• Python Recursion

---

The factorial of a number is the product of all the integers from 1 to that number.

For example, the factorial of 6 is 1*2*3*4*5*6 = 720. Factorial is not defined for negative numbers, and the factorial of zero is one, 0! = 1.

Factorial of a Number using Loop

# Python program to find the factorial of a number provided by the user.

# change the value for a different result
num = 7

# To take input from the user
#num = int(input("Enter a number: "))

factorial = 1

# check if the number is negative, positive or zero
if num < 0:
   print("Sorry, factorial does not exist for negative numbers")
elif num == 0:
   print("The factorial of 0 is 1")
else:
   for i in range(1,num + 1):
   factorial = factorial*i
   print("The factorial of",num,"is",factorial)

Output

The factorial of 7 is 5040

Note: To test the program for a different number, change the value of num.

Here, the number whose factorial is to be found is stored in num, and we check if the number is negative, zero or positive using if...elif...else statement. If the number is positive, we use for loop and range() function to calculate the factorial.

iteration	factorial*i (returned value)
i = 1	1 * 1 = 1
i = 2	1 * 2 = 2
i = 3	2 * 3 = 6
i = 4	6 * 4 = 24
i = 5	24 * 5 = 120
i = 6	120 * 6 = 720
i = 7	720 * 7 = 5040

---

Factorial of a Number using Recursion

# Python program to find the factorial of a number provided by the user
# using recursion

def factorial(x):
"""This is a recursive function
to find the factorial of an integer"""
if x == 1 or x == 0:
    return 1
else:
    # recursive call to the function
    return (x * factorial(x-1))

# change the value for a different result
num = 7

# to take input from the user
# num = int(input("Enter a number: "))

# call the factorial function
result = factorial(num)
print("The factorial of", num, "is", result)

In the above example, factorial() is a recursive function that calls itself. Here, the function will recursively call itself by decreasing the value of the x.

---

Also Read:

• Python Program to Find Factorial of Number Using Recursion

Before we wrap up, let’s put your understanding of this example to the test! Can you solve the following challenge?

Challenge:

Write a function to calculate the factorial of a number.

• The factorial of a non-negative integer n is the product of all positive integers less than or equal to n.
• For example, for input5, the output should be 120

1. def factorial(n):

Python Program to Check Prime Number

To understand this example, you should have the knowledge of the following Python programming topics:

• Python if…else Statement
• Python for Loop
• Python break and continue

---

A positive integer greater than 1 which has no other factors except 1 and the number itself is called a prime number. 2, 3, 5, 7 etc. are prime numbers as they do not have any other factors. But 6 is not prime (it is composite) since, 2 x 3 = 6.

---

Example 1: Using a flag variable

# Program to check if a number is prime or not

num = 29

# To take input from the user
#num = int(input("Enter a number: "))

# define a flag variable
flag = False

if num == 0 or num == 1:
print(num, "is not a prime number")
elif num > 1:
# check for factors
for i in range(2, num):
    if (num % i) == 0:
        # if factor is found, set flag to True
        flag = True
        # break out of loop
        break
# check if flag is True
if flag:
    print(num, "is not a prime number")
else:
    print(num, "is a prime number")</code></pre>


Run Code



Output



29 is a prime number



In this program, we have checked if num is prime or not. Numbers less than or equal to 1 are not prime numbers. Hence, we only proceed if the num is greater than 1.



We check if num is exactly divisible by any number from 2 to num - 1. If we find a factor in that range, the number is not prime, so we set flag to True and break out of the loop.



Outside the loop, we check if flag is True or False.




If it is True, num is not a prime number.



If it is False, num is a prime number.




Note: We can improve our program by decreasing the range of numbers where we look for factors.



In the above program, our search range is from 2 to num - 1.



We could have used the range, range(2,num//2) or range(2,math.floor(math.sqrt(num)+1)). The latter range is based on the fact that a composite number must have a factor less than or equal to the square root of that number. Otherwise, the number is prime.



You can change the value of variable num in the above source code to check whether a number is prime or not for other integers.



In Python, we can also use the for...else statement to do this task without using an additional flag variable.