How would you reverse a string in Python

Reversing a string in Python can be done in several ways. Here are the most common methods:

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1. Using Slicing

The slicing technique with the step parameter -1 is the most Pythonic way to reverse a string.

# Example
string = "hello"
reversed_string = string[::-1]
print(reversed_string)  # Output: "olleh"

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2. Using the reversed() Function

The reversed() function returns an iterator, which can be converted back into a string using ''.join().

# Example
string = "hello"
reversed_string = ''.join(reversed(string))
print(reversed_string)  # Output: "olleh"

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3. Using a Loop

You can iterate through the string in reverse order and build the reversed string manually.

# Example
string = "hello"
reversed_string = ''
for char in string:
    reversed_string = char + reversed_string
print(reversed_string)  # Output: "olleh"

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4. Using a Stack (List)

Strings can be treated as a stack (last-in, first-out) by converting the string to a list and then using the pop() method.

# Example
string = "hello"
stack = list(string)
reversed_string = ''
while stack:
    reversed_string += stack.pop()
print(reversed_string)  # Output: "olleh"

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5. Using Recursion

A recursive function can reverse a string by taking the first character and appending it to the reversed rest of the string.

# Example
def reverse_string(s):
    if len(s) == 0:
        return s
    return s[-1] + reverse_string(s[:-1])

string = "hello"
reversed_string = reverse_string(string)
print(reversed_string)  # Output: "olleh"

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6. Using str.join() with List Comprehension

This approach reverses the string by using a reversed list comprehension.

# Example
string = "hello"
reversed_string = ''.join([string[i] for i in range(len(string)-1, -1, -1)])
print(reversed_string)  # Output: "olleh"

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Performance

• Slicing ([::-1]) is the fastest and most commonly used method in Python because it is optimized internally.
• reversed() is slower due to the creation of an iterator.
• Loop-based methods and recursion are generally less efficient but demonstrate algorithmic approaches.

For simplicity and readability, slicing is the recommended method in most cases.