Python Reverse A String

In this article, we will discuss reversing a string in Python. We will look into different approaches.

1. Naive method

In this naive approach, we will loop through each letter in the string and joins them to form a reverse string as shown below.

def reverse_string(txt):
  rev_text = ""
  for letter in txt:
    rev_text = letter + rev_text 

  return rev_text

rev_str = reverse_string("hello")
print(f"Reversed string : {rev_str}")

Output

Reversed string : olleh

2. Reverse using list.reverse()

In this approach, we will convert a string to a list, then reverse it using the list.reverse() method. Again the list is converted back into a string.

def reverse_string(txt):
  lst_txt = list(txt)
  lst_txt.reverse() 
  rev_text = "".join(lst_txt)
  return rev_text

rev_str = reverse_string("apple")
print(f"Reversed string : {rev_str}")

Output

Reversed string : elppa

3 . Reverse using the reversed method

The string is revered using the inbuilt Python method reversed, it will return a reverse iterator. It is converted back to a string.

def reverse_string(txt):
  rev_iter = reversed(txt)
  rev_text = "".join(rev_iter)
  return rev_text

rev_str = reverse_string("cloud")
print(f"Reversed string : {rev_str}")

Output

Reversed string : duolc

4. Reverse using the string slicing

This is the simplest method to reverse a string in Python. A string slice has the following format

string[start:stop:step]

• start: start position of the character
• end : End position of the character
• step: Number of characters to jump after an iteration

To reverse a string we can simply use string[ : :-1], which will process the string in the reverse order (because step is -1) and returns the reversed string.

>>> txt = "hello"
>>> txt[::-1]
'olleh'

5. Reverse a string using list comprehension

In this method, we will use list comprehension to reverse the string in Python. The range function is used to generate an index of the character. We will use the reversed index from range(len(txt)-1, -1 , -1) function.

def reverse_string(txt):
  rev_iter = [ txt[i] for i in range(len(txt)-1,-1,-1)]
  rev_text = "".join(rev_iter)
  return rev_text

rev_str = reverse_string("happy")
print(f"Reversed string : {rev_str}")

Output

Reversed string : yppah

One-liners to reverse a string in Python

We can use the following one-liners to reverse a string.

>>> txt = "hello world"
>>> txt[::-1]
dlrow olleh
>>> "".join(reversed(txt))
dlrow olleh

Conclusion

There you have it, different methods to reverse a string in Python.