How do I reverse a string in Python?

Slice it with a step of -1.

word = "stressed"
print(word[::-1])

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Why [::-1] works

A slice is [start:stop:step]. Leave out start and stop and you get the whole string; a step of -1 walks through it backwards. Other steps work the same way:

letters = "abcdefgh"

print(letters[::2])     # every second letter
print(letters[::-2])    # every second letter, from the end
print(letters[2:5])     # positions 2, 3 and 4

aceg
hfdb
cde

The readable alternative

reversed() returns the characters in reverse order, and "".join glues them back into a string. Longer, but someone new to Python can read it:

word = "stressed"
print("".join(reversed(word)))

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reversed(word) on its own is not a string; printing it shows <reversed object at 0x...>. The join is what turns it back into text.

A common use: palindromes

def is_palindrome(text):
    letters = [c.lower() for c in text if c.isalnum()]
    return letters == letters[::-1]

print(is_palindrome("Never odd or even"))
print(is_palindrome("Python"))

True
False

Slicing works on lists too, as you can see. Removing spaces and punctuation first is what makes "Never odd or even" count.

Reversing words, not letters

sentence = "the quick brown fox"
print(" ".join(sentence.split()[::-1]))

fox brown quick the

One limit worth knowing: [::-1] reverses code points, not what you see as letters. An accent stored as a separate combining mark, or an emoji built from several parts like a family or a flag, comes apart when reversed. For names and plain words it never matters; for user-generated text with emoji, it can.