Python Exercise: Reverse a string

Last update on April 22 2025 12:58:11 (UTC/GMT +8 hours)

4. Reverse a String

Write a Python program to reverse a string.

Sample String: "1234abcd"
Expected Output: "dcba4321"

Sample Solution-1:

Python Code:

# Define a function named 'string_reverse' that takes a string 'str1' as input
def string_reverse(str1):
    # Initialize an empty string 'rstr1' to store the reversed string
    rstr1 = ''
    
    # Calculate the length of the input string 'str1'
    index = len(str1)
    
    # Execute a while loop until 'index' becomes 0
    while index > 0:
        # Concatenate the character at index - 1 of 'str1' to 'rstr1'
        rstr1 += str1[index - 1]
        
        # Decrement the 'index' by 1 for the next iteration
        index = index - 1
    
    # Return the reversed string stored in 'rstr1'
    return rstr1

# Print the result of calling the 'string_reverse' function with the input string '1234abcd'
print(string_reverse('1234abcd'))

Sample Output:

dcba4321

Explanation:

In the exercise above the code defines a function named "string_reverse()" that takes a string as input and returns its reversed version using a while loop and string manipulation. The final print statement demonstrates the result of calling the "string_reverse()" function with the input string '1234abcd'.

Pictorial presentation:

Flowchart:

Sample Solution-2:

Python Code:

# Define a function named 'reverse' that takes an iterable 'itr' as input and returns its reverse
def reverse(itr):
    # Using slicing with [::-1] reverses the input 'itr' and returns the reversed version
    return itr[::-1]

# Initialize a string variable 'str1' with the value '1234abcd'
str1 = '1234abcd'

# Print the original string 'str1'
print("Original string:", str1)

# Print the reversed string obtained by calling the 'reverse' function with the string '1234abcd'
print("Reverse string:", reverse('1234abcd'))

# Change the value of 'str1' to 'reverse'
str1 = 'reverse'

# Print the original string 'str1'
print("\nOriginal string:", str1)

# Print the reversed string obtained by calling the 'reverse' function with the string 'reverse'
print("Reverse string:", reverse(str1))

Sample Output:

Original string: 1234abcd
Reverse strig: dcba4321

Original string: reverse
Reverse string: esrever

Explanation:

In the exercise above the code demonstrates the use of a "reverse()" function that utilizes slicing ([::-1]) to reverse a given input iterable. It then applies this function to reverse both the string '1234abcd' and the string 'reverse' and prints their original and reversed versions.

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python function that uses slicing to reverse a given string.
Write a Python function that iterates over the string in reverse order using a loop and constructs the reversed string.
Write a Python function that converts the string to a list, reverses the list, and joins it back into a string.
Write a Python function that uses recursion to reverse a string and returns the result.

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Python Code Editor:

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