KTU
2024 Scheme
S1-Alg thinking with python
String Operations

String operations using python

Aim

Create, concatenate, and print a string and access a sub-string from a given string.

Algorithm

  1. Start
  2. Input a string from the user
  3. Take the choice input from the user
    • Validate the choice input
    • If the choice is 'e', exit the program
    • If the choice is not one of the 3 choices, print "Invalid choice" and continue
    • else, go to step 4
  4. Perform the operation
    • If the choice is 1, concatenate the string
    • If the choice is 2, access a substring
    • If the choice is 3, print the string
  5. End

Program

string_operations.py
# Function to concatenate two strings
def concatenate_strings(string1, string2):
    return string1 + string2
 
# Function to derive a substring from a string
def access_substring(string, start_index, end_index):
    return string[start_index:end_index]
 
# Input string
string_1 = input("Enter a string: \n")
 
while(True):
    # Input the choice from the user
    choice = input("Enter 1 to concatenate the string, 2 to access a substring, 3 to print the string \nor press 'e' to exit the program: \n")
 
    # Validate the choice input
    if choice.lower() == 'e':
        break
    elif choice not in ['1', '2', '3']:
 
        print("Invalid choice")
        continue
    else:
 
        # If the choice is 1, concatenate the string
        if choice == '1':
            string_2 = input("Enter another string: \n")
            concatenated_string = concatenate_strings(string_1, string_2)
            print(concatenated_string)
 
        # If the choice is 2, access a substring
        elif choice == '2':
            start_index = int(input("Enter the start index: \n"))
            end_index = int(input("Enter the end index: \n"))
            sub_string = access_substring(string_1, start_index, end_index)
            print(sub_string)
 
        # If the choice is 3, print the string
        elif choice == '3':
            print(string_1)

Sample Input/Output

Enter a string:
Hello
Enter 1 to concatenate the string, 2 to access a substring, 3 to print the string
or press 'e' to exit the program:
1
Enter another string:
World
HelloWorld
Enter 1 to concatenate the string, 2 to access a substring, 3 to print the string
or press 'e' to exit the program:
2
Enter the start index:
0
Enter the end index:
5
Hello
Enter 1 to concatenate the string, 2 to access a substring, 3 to print the string
or press 'e' to exit the program:
3
Hello
Enter 1 to concatenate the string, 2 to access a substring, 3 to print the string
or press 'e' to exit the program:
e

Explanation

  • The program takes a string as input from the user.
  • The program then takes the choice input from the user.
  • If the choice is 1, the program concatenates the string.
  • If the choice is 2, the program accesses a substring.
  • If the choice is 3, the program prints the string.
  • The program continues to take the choice input until the user chooses to exit the program.

Complexity Analysis

The time complexity of the program is O(1) as the program performs a fixed number of operations irrespective of the input size.

The space complexity of the program is O(1) as the program uses a fixed amount of extra space irrespective of the input size.

How can you improve this program?

  1. You can add more string operations like finding the length of the string, converting the string to uppercase or lowercase, etc.
  2. You can add more validation checks for the input strings and indices.
  3. You can add error handling for invalid inputs.

Summary

In this tutorial, we learned how to create, concatenate, and print a string in Python. We also learned how to access a substring from a given string. This program demonstrates the basic string operations that can be performed using Python.

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